so heres the deal when im just crusing along a low throttle angles the car stumbles. if i give it gas or let off its fine. im guessing its the tps.

the car is an s4 na mods are tb mod(awaiting to undo that). no emissions, and a street port.

o and im getting a strange waxy build up in the filler neck. its like white and i guess waxy. im not really loosing any coolant or anything, could it just be from condensation in the morning??

 

That white ish looking stuff i get too. Have always seemed to get it. Especially if I start driving before the car can warm up. Mine smells a little like gas, not sure if yours does.

Does your car idle fine? If not, I would probably check for air leaks. You mentioned emissions removed. Sometimes little leaks pop up.

Also, take an analog multimeter to your TPS and see if there are any breaks in the TPS range.

Hook TPS up. Slowly push the throttle down, and see if the needle slowly raises from 1k OHM up to I think 6.5k OHM. If it isn't smooth, there is probably a problem. Like, if the needle on the meter fluxuates suddenly.

If you can find the spot it fluxuates, verify by pushing the throttle in and out of that spot and watch the needle on the multimeter.

A digital multimeter won't work for this. Mostly because they try and range, etc. Analog meters can be purchased for cheap, approx. $10-$15 and are used a lot when trouble shooting electrical problems. Good investment.