My 3400 idles good, when i rev it and hold it at a constant rpm it begins to stall out and the fumes could kill you. If I drive it like this it runs like a bat out of hell but when I get to a constant speed it starts running like hell, when i give it a little throttle it responds good, but when the constant speed comes back it starts running bad. If I drive it like this for say 10 minutes my check engine light comes on and the car instantly runs great, but doesnt seem to perform as good or pull as hard. Any ideas what this could be?? THanks