Hesitation problem with 1994 4Runner

I'd greatly appreciate some help with diagnosing a problem with my 94

4Runner SR5, 5 spd, 3.0 V6. I had this vehicle into the dealer I had been going to for 8 years now, and they said "no problem found" on all my complaints. After another dealer found the problem in my A/C, and I just had another mechanic replace my original clutch (142,000 miles), the vehicle still has an acceleration hesitation problem. The half decent second dealership said it may be related to the aging clutch, but now that it's been replaced, the hesitation is still there. This dealership gave me an expensive tune-up (should have seen this coming), and de-carbed the engine. New distributor cap, rotor, wires, plugs, etc., no difference. I made them replace the O2 sensor (I provided it), as they say they only replace them after the check engine light comes on. Still no difference.

During acceleration, the engine seems to start pulling OK after about 3,000 RPM; I also notice sluggishness when travelling in slow conditions in 3rd gear, where it never used to be a problem. Now I am forced to downshift. I used to get over 18 MPG, last fill-up I got 15. Is this EGR related? Is the catalytic converter plugged?

Any help would be greatly appreciated. It's hard to find a decent honest mechanic, and I spend a lot of time driving this vehicle. I just want it to be right. This is the first time it's had any problems since we bought it new.

Thanks.

Bill Chesapeake, VA