trouble starting on hill or under load in 1st

[explorerfriend]

I have a '95 explorer 4.0 OHV 5spd, and i have had a lot of trouble starting in 1st gear on a hill or when carrying lots of people on a level road, since...i don't know when? but even if i get the car to 2000rpms and pulled the clutch to start, it will drop to 500rpms (sometimes even more and i will get a nasty clatter) and it takes a second or two for the engine to be able to pull the car(no matter how much gas i give it). i got a little bigger tires and wheels (225/70r-15---->245/70r16) and didn't re-gear. would that do it? I have no unneccesary weight in the car, idle is fine , and i just got my camshaft position sensor replaced ( a good $389) b/c the cel had been on for the past 6 yrs and would never allow me to connect to the pcm (EEC IV). the cel is now off, and doesn't give any codes.

so really i am just having problems acceleration to maybe 4-8 mph, after that the engine can really pull!

does anyone else have this problem or maybe know of a solution