2002 GLS losing power

Hello, i have had my VW for four years now and it has been great. However, recently I have had brake problems. It cost me over $400.00 for the work on just the front. The rotors warped causing friction to build until the brakes just locked up. Has anyone had anything similar happen to their golf? Anyway I thought whatever, I will just get the brakes fixed. It was a safety issue. The brakes would lock up in traffic nearly causing an accident on a couple of occasions even on the way to the dealer. VW just treated this as routine. I have had a 1969 beetle and never NEVER had to do ANYTHING to the brakes, why the big difference in quality??? Anyway aside from getting a lawyer to confront VW with these SOFT rotor problems I had it fixed. But, the power problem is still appearing. After the car is driven for any amount of time, running errands or whatever... It starts to feel like it is being held back by something. Maybe not mechanical, Maybe a sensor somewhere needs replacement? But NO check engine light as if everything is normal. Can someone please get back to me on this? :uhoh:

engine? transmission?

Thanks for replying.
Thats just it I do not know what is the problem but I can only say that it feels like something is holding the car back from accelerating. This is what I have done. Regular oil changes using synthetic oil. Pentosin. Recent brake service. including rotors and pads replacement. K&N filter, Installation of air ducts to front grill directly from air box. No kinks, nice and open. i have retained the stock air intake so I can switch back and forth to the modified air box and stock within 5 minutes. MAF cleaner. I dont know what else to do without major money investments.