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96 vw jetta engine lag

i figured it couldnt hurt to ask and see who might be able to help me out on this topic. my 96 vw jetta (2.0l 8v) has an inconsistent lag. i say inconsistent because some days it wont and some days it will. i had an issue with a few wires being rubbed (to my throttle position sensor and mass air flow sensor which caused some serious surging and bucking. i solved that problem but am kinda stumped on this one. it seems almost as if its worse when its been driven for a while, i usually drive about 50+ miles in a trip to work or see family so i notice it during the rides. though i also noticed that usually after being on the highway for a while (30 of the 50 miles) and then going back to city driving it runs pretty crisp for a bit. i almost feel like its being flooded slightly during take off. the lag takes place usually between acceleration from idle to about 3000 rpm, then after that it runs crisp. im not sure if its from a bad sensor or possibly another wire exposed. im just kinda stumped. when i found the other exposed wires i did a good tune-up; plugs, wires, distributor cap and rotor, ignition coil, fuel filter, oil and filter and the air filter. it has 198k miles on it but runs like a champ and starts right up, not to mention i love the car and just simply want it running ship shape. i dont know if the timing belt was changed and that has been on my list of things to do but have been holding off since i really dont wanna do it myself. but i wasnt sure if maybe the belt (if it is) aged is slipping or has slipped a tooth. or like i said before maybe i have a bad sensor that is throwing off my air fuel mixture. i dont have the check engine light on since ive fixed the mentioned exposed wires so theeres no codes to check. also wanted to let you know a couple days ago when i got in it and went for a ride it ran beautiful, felt like it was running 100% and that lasted probably 2-3 days until i noticed it lagging again. my definition of the lag is during take off i have to throttle into it a bit like i have a full passenger load almost but it could be just me (its a 5 speed) and you can feel it (if i keep the throttle stationary during take off) it will actually jump a tad(after the clutch has been fully released and it takes a second before) it catches itself which is why i said it almost felt like flooding then leveling out. also during acceleration it will suffer from some power loss until i get higher in rpm (approx 3-4000) before it feels crisp running again. any advice or help would be REALLY appreciated!