I have a 91 bmw 5251A sedan and when ever i drive down the highway there are high speed vibrations when i accelerate and smootheness when i cruise. i have no idea where its coming from. when i rev it to 2k in idle it vibrates. i have a feeling that its a ign/fuel issue. the car was my parents and it has only 65k on the clock. with in the last year it got a new iacv, o2, sensor, rims and tires. with in the last 2 months when it all started it got new bmw plugs, new bremi coils and boots. i went through the diag procedures in the bentley manual and everything checks out except the cps. the cps reading is at 542 ohms instead of 1280 ohms. i searched around and others have the same issue and there was never a clear resolution. the car always got 93 octane gas, oil every 7k with full synthetic. it also got a new set of front chocks within the last 2 months. i thought it might have been the shock install but i checked everything out and it was fine. i had the wheels rebalanced and all. where should i start looking to resolve this issue?