okay i picked up a speed demon 850 from a swap meet. i went threw it and it and it idles way better than the edelbrock. what cauese the stumble. if i stall the car up to 3000 it takes of great but when crusing or in park if i dead stomp it it cuts out and then revs fine to 7000. would that be the shooters it has 31 primary and secondary. would it be the pump cam?