When I drive my car at about 2500 rpms it acts like it doesnt get enough gas and jerks( it is a standard and it feals like its down shifting but),that kinda jerking but not getting fuel and at first my friend thought it was the air filter, then a shop told me the altanator, and an 02 sensor, i had the altanator tested 3 times it was good. so my friend thinks it is the IAC valve could this be the problem and how can i fix it. thanx in advance