1999 jetta gls 2.0.auto trans. randomly decides the gas petal is useless. i keep my foot on the gas petal with steady pressure. the rpm’s go crazy, revving and almost staling to revving again. when the rpm’s are not going crazy, the car will not go faster then 30mph. it seems there is no rhyme or reason to why it starts doing it. normally if it does it and i let the car sit awhile it’ll run fine for a couple days. but now its won’t stay started. it starts normal but then shakes and stalls. i recently had work done one the timing belt, cam shaft sensor and mass air flower sensor. the check engine light is on and throws a code for another air sensor. help!
[i] the check engine light is on and throws a code for another air sensor. [/i] That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the code read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
[i] i recently had work done one the timing belt, cam shaft sensor and mass air flower sensor.[/i]
Who did the work on the timing belt? Can we assume they replaced the timing belt? Was it replaced because it was due based on miles or time?How old is that battery?
You might want to have it tested, if its older than 4 years.
German cars tend to be very sensitive to batteries that are getting to be borderline.
BC.
i did get it checked out and it threw a code for an ac sensor. if thing thing would stay running i would get it checked out again to see if maybe it has a different one now.
and a local shop did the work. my timing was 6 teeth outta time and then belt was frayed. this car is awesome when it works but when one thing goes wrong it everything else goes too. -_-
hummm i have not checked the battery. i shall do that. i think i can afford a battery way better then a sensor on a students budget 
Manual or automatic transmission? Your description sounds like either a clutch or automatic transmission slipping. If automatic, check the fluid level and, if low, top it up with the proper fluid and hope for the best. If manual, and it’s the clutch slipping, the solution is to replace the clutch and either replace or resurface the flywheel. Do not neglect the flywheel.
i’m reading thro my haynes manual and i agree it could be the clutch . under troubleshooting (engine speed increases with no increase in vehicle speed) it takes me to the clutch thing. and my car doesn’t have a dipstick for the transmission or if it does no shop has been able to find it. i changed the trans. fluid soon after i got it and it was black an gritty! anyway my problem is, its costs about $80 to get everything i need for a trans fulid changed. i don’t have $80. 
ok i have the codes. PO112 and P1128
P0112 - Intake Air Temperature Circuit Low Input
P1128 - MAP Lower Than Expected
The MAP is the Manifold Air Pressure sensor, usually hooked to the intake plenum with a vacuum line. This is different than the Mass Air Flow sensor, usually in the air intake line near the air filter. The Intake Air Temp sensor on this car may also be located on the intake plenum.
sooooo how do i fix it? and how much is it gonna cost me.
If you have a Haynes manual, it should have test procedures to check the sensors and replace if necessary.