I have a 1990 Mustang GT Convertible with 94K miles. Car is stock, I bought it about 4 weeks ago. First issue I noticed was it wasn't coming up to normal temperature. Now temperature is normal but the car bucks from a stop and durins acceleration. So I changed the thermostat (fun!). I assumed the carbon build up was pretty bad so I Did the seafoam through the vacuum lines thing. Better but still not quite right. Changed fuel filter, no change. Replaced spark plugs (that were gapped like .070) no change. The car starts and idles fine. If you rev the engine 2000-2500 it will hesitate. Sometimes when driving when I press the gas it will rev up to like 3000 rpm with no increase in power. Then other times there is no hesitation but it does not have typical 5.0 power. Help please!