2 thing i would check. listen near the intake manifold and see if u can hear any air leaking out. mine did that b/c when the shop i went to put in my motor they screwed up putting back the manifold. another thing is it prolly would be that the throttle valve is stuck open a little, that would make the ecu think that your on the gas when ur realli not so adjust the throttle cable so that the valve closes. thats all that i can think of