Give the computer some time to adjust to the new MAF sensor, at lest 3 drive cycles.
It matches RPM and gps
Computer already knows how much air a 5.0l engine uses at any given RPM, MAF sensor is to fine tune that for altitude and temp.
IAT also does temp but so does MAF just by the air flow, and IAT compared to MAF compared to RPM table can calculate reasonably close barometric pressure

Normal for STFT to jump up that high when accelerating, when cruising it should drop back down

 

Ok so the first thing I noticed is when I started her up cold she idled nice. Took her in shop to change that fuel filter, lol, had to break filter to get broken piece of tool out of the connect. then the lil **** still wouldn't come out. I wound up putting a hose on front, cutting as close to the end of metal fuel line, got her together and drove home. she runs ok except she bucked a couple time when she shifted either to 3rd or overdrive, my bet 3rd. she even backfired once then I jumped on her and she took off. got home and hooked up scanner and got a surprise. no codes except a pending one...insufficient vacuum to egr.... lol, everything is new but ill find that one. thanks for all your help

 

Hopefully new fuel filter will give you better flow, good work

 

Thanks, lol, ii drove the truck home with new filter and maf sensor. It seemed to go ok til about 40 mph then actually bucked a lil...didn't want to go so I backed off. As I got closer to home it did so again, I hit it harder and it popped back thru intake then took off. I thought it was about egr insufficient flow bur mech says that won't give drivability issue. It started with maf so I'm going to put old one back on to see if that stops, if it doesn't then it's not maf. Me and my engine r having fun playing games with each other...lol

 

Here's a thought, or maybe not, could it be the maf sensor from the guys truck..it's a 2000 explorer or mountaineer..if it's a return less fuel system which might hav different fuel pressure? Maybe it's not calibrated for my setup and it gets by til truck is at a higher speed then it's got fuel off at higher speed?

 

The two wouldn't be related.
MAF sensor data must make sense to the computer, it knows the engine displacement so knows approximately how much air will be coming in passed the MAF sensor at any given RPM and throttle position.
MAF is basically used for altitude and air temp, but if incorrect it can cause engine to buck or lose power because computer would be running engine for a higher altitude or air temp
Now a MAF sensor only samples about 10% of the air flowing passed it, so any error would be multiplied 10 times when computer converts it to full air flow weight.

Fuel pressure is also known/told to computer at the factory, and computer knows how much gasoline weighs, so it knows how much gasoline weight will flow out of an injector if it is open for 10 milliseconds, as an example

So no real connection there.

MAF gives computer Grams of air(weight) per second
Air/fuel ratio is 14.7:1 for gasoline, this is a weight ratio
So for every 14.7 grams of air, computer will add 1 gram of gasoline

If MAF is incorrect or fuel pressure then there would be a problem with computers calculated results, because it is based on bad info, garbage in garbage out, lol, old computer saying

But computer is adaptive, it will adapt to lower incorrect air flow as MAF gets dirty and lower fuel pressure as pump gets old, this is what Long term fuel trims(LTFT) are for.
But at some point computer will notify driver when data gets too far out of range
This is why there are no exact numbers of good and bad, about and approximate are the only thing that can be used with this
When you put on a different MAF sensor computer doesn't "know it", so engine could run oddly for a few days until LTFT is adapted to new MAF data.

If there were exact numbers then vehicles would be in the shop every 6 months or so, for cleaning sensors or replacing them, lol.
Just like in the old days with points in a distributor, or having to readjust the carb

 

Ok got ya, I came home and put old maf on to see if that got rid of the pop or backfire crap. it was worse, was sitting at red light and idling decent..all of a sudden idle drops a bit and she barely limped home. I put newer maf back on, battery neg off a good 15 min. took it for a drive, ran decent, hit it once..heard a pop not sure if its exhaust or what but then it took off again. got home and put scanner on it. checked the codes...my old friend is back..running lean...the thing I'm noticing is the grams per sec dropped and the short term fuel trim went way up, like 39%. when the maf shows higher gps the fuel trims are good. I may be living with this issue..lol. if she will start normal in the morning or whenever, I may have to live with a lean condition? I'm going to look at the plugs sat morning. the scanner says one possibility of the lean thing is badly worn plugs? a funny thing here is my 97 mountaineer maf sensor isn't made by ford anymore and its about $65 to $115 at parts store but they are all re man...the one I have in it is a 2000 mount/explorer , not sure which, but its $55 at the dealership, its a motorcraft and its brand new. well, I'm going to give it a rest til 2moro..lol

 

Ok I drove it to work today, told the mech how its running with it popping when it hits about 40 and in higher gear of course. he said it sounds like a lean fuel backfire. he asked if I had ever checked fuel pressure. I told him I thought the book I had on motor said its supposed to be 35 to 42, but its at 30. he said that's livable..i told him and I don't think ive mentioned this but when I start it with gauge on it the pressure takes like 8 to 10 seconds to get to 30 psi. he said it should be there almost instantly..he feels the fuel pump is the problem. told me if I check it again to take vacuum line off regulator, the gauge should go up a good 5 psi. she is running good except you can feel the difference once it gets to 3rd gear or about 40mph. otherwise its good.

 

Yes, that would make sense

The FPR is set for about 40-45psi, so spring inside will be pushed open if pressure gets that high, normally with the vacuum assist it opens it before 40psi.

I would add to that test, see what pressure is at idle with vacuum hose removed and hose plugged.
Then raise RPMs to 2,500 and hold it there

Good fuel pump should push open good FPR at 40-45psi and have enough head room to keep it there at 2,500RPM.

If pressure only goes to 35psi then FPR could be weak, like mechanic said, and that is fine, but test it at 2,500rpm.

Another thing I have seen people do is to get a longer hose extension for the Pressure gauge and run it out the front and over onto the hood so they could watch the pressure while driving.
They duct taped it down, lol