I don't really know what to call this so I'm going to attempt to explain. When I'm at a stop I keep my truck in neutral ( I drive a manual) when I put it in first and even out the clutch and the gas it kind of just lurks forward and the rpms drop to around 1200. I have to push the pedal to the floor and it still feels like a ton of lag. Once I get to around 2500 rpms then I start to pick up some speed and I can shift later around 3500. It's even worse lag when the AC is on. Is this just classic 4 banger power? I doubt I'm evening the clutch and gas wrong cause I've been driving a manual for about 4 years. Any ideas of what this could be?

 

First clean the MAF(mass air flow) sensor, should be done every 2 years, takes about 15min first time then 5 minutes there after

I would test(not replace) the TPS(throttle position sensor).
TPS tells computer when you want to accelerate, it serves the same purpose as the Accelerator Pump did on a carb.
Like ALL sensors, these rarely fail but rarely isn't never.
It has 3 wires
5 volts, from computer
1 to 5volts from TPS back to computer
Ground

Center wire is the one you want to test, the 1 to 5 volt wire that tells computer what you want to do.
Use a sewing pin to pierce the center wire
Set volt meter to DC volts
Turn key on, engine off
Put Black meter probe on a ground, or battery "-"
Put Red probe on sewing pin in center wire
Should read .69 to .99 volts

Hold Red probe on pin and slowly open the throttle manually, voltage should slowly increase, no jumping around or dropping, at wide open throttle you should see 4.5 to 5volts
If so all is well with TPS.

Could also be a vacuum leak, after engine is warmed up and idling, unplug the IAC valve, RPMs should drop down to 500 or engine may even stall, either is good, it means no vacuum leaks.
If idle stays 700 or higher then you have a leak.

 

I'll start this weekend by checking the vacuum leak and let you know how it goes. Thanks!