I have a 2001 pontiac grand prix gt NA 3.8 w/ a WAI and flowmaster mufflers the car has 115,000+ miles on it and I have been feeling a strong vibration when the car is stopped at a light, I have changed the fuel filter, air filter(w/ a WAI), spark plugs, spark plug wire, sea foamed it, used Chevron fuel system cleaner, replace pcv valve, change oil(Penzoil High Mileage 10w-40), used Engine Restore(the oil additive) but there is still a vibration which makes me want to look at the engine mounts, is there anything else I could have missed? Any ideas on where the vibration is coming from?
P.S it's not rocking back and forth just alot of vibration main felt from the steering wheel.
Thanks, for the help in advance