I have a 91 firebird v6 3.1 and when I start it it idles high and drops down to about 800 but after driving and it warmed up and I stop at a light it will idle up to about a grand and I will hit the gas and it will drop back down to 8 for a couple mins and slowly rise again and when I throw it in Neutral Itll jump to about a 1500 someone help please my gas milage suxz