Toyota Repair: Previa Hesitating, throttle position sensor, sensor tps

Question
Ted,
My 91 Previa intermittently hesitates before accelerating.  It seems to be completely random and can happen at any speed.  Most of the time it works fine.  Previously, I had some stalling problems but I just had the purge vent solenoid replaced, and so far so good.  I believe the hesitating is unrelated.  It started the day after I had a tune up and I'm afraid I may have received a bad part.  I had the following parts replaced when the van was tuned up: fuel filter, spark plugs, distributor cap and rotor, PCV valve, and a new set of wires.  Could any of these new parts be the cause of my problem?  Your advice is appreciated.
Stephanie

Vehicle info:  1991 Toyota Previa AllTrack with automatic transmission.  156,000 miles and counting.  Had new exhaust system put in last year.  Recently replaced the shocks and struts.  

Answer
There were some problems with the wiring connector on the throttle position sensor(TPS) on the throttle body that can cause this problem, the wires would break inside of the insulation and cause driveability problems, I'm not sure if this is the case but it may be worht a try to replace the connector with the wire subharness.
It comes in a repair kit which consists of the connector and a subharness which is wired into the existing harness, your toyota dealer should be able to help in locating the part, I don't have the part number, it's called the throttle posistion sensor harness repair kit, if you have trouble locating it I can give you a part number, again, I'm not totally sure this is what the problem is but is was a common problem in the past.