I am having another problem with my 90 deville 4.5 My acceleration is horrible. for example when i am on the highway to get my car to speed up i have to floor the gas all the way down then start letting up off of it slowly and the then car goes. My gas milage is horrible! my average is 11.5 my mpg guage reads between 0 and 4 when i floor it and about 8 when im cruising unless im going over 40 at a constant speed then it reads 12-18. The car got way better gas milage when i bought it. I have a friend with an 89 deville he gets 26 on the highway. What could my problem be??? I have new plugs, wires, fuel filter, tps, Ecu, new ground wires,o2 sensor and a new idle control motor. Any ideas???, suggestions???