Engine miss
 

New here and thanks for all the help I've picked up just reading.
I've got a 99 mazda b4000, 4.0 engine, auto trans, 4wd, 170,000 miles that
runs great except when the engine is between 1500 and 2200 rpm and under load. It runs great on the flats but once I start up an incline and the engine starts to pull it misses pretty bad. I've read through all of the posts that looked like the same problem but didn't find anything quite like this. There's no CEL, I've cleaned the IAC and it makes no noise, Seafoamed the engine and ran 2 tanks of seafoam treated gas. Last night I disconnected the MAF which didn't help but I'll clean it anyway. I changed the fuel filter too. So I'm working my way through the easy cheap stuff and would like some ideas on what to check or replace next. Thanks!

It would be prudent to look at the spark plugs gap/condition....since you didn't mention those.

You may also want to spray a mist of water on the plug wires at night, with the engine running, then revving, to look for arcing from the plug wires.