at idle the car is fine and the rpm's are constant but when i try to hold the car at say 4k the motor surges. or when i am driving and try to cruise at one even speed the motor either wants to accelerate or decelerate. it will not stay at one speed. could it be the tps or iac? it is a LS engine.

 

first of all, you need a visual inspection under your hood, make sure all hoses are tight, and everything around your throttle body is where its supposed to be, thats the general area that will affect touchy things like that. second what check engine lights are you showing? im sure some kind of malfuction like that must have thrown a code, jump the service connector under your glove box and see what its saying..

 

it is throwing a code 10

 

so why don't you fix your iat then?