car runs fine when throttle is 1/4 to wide open. But when light cruising, it sputters all over the place. If completely off the gas, like going down hill or something, then I give it throttle of anykind, it falls on it's face and backfires. I usually have to pull over and wait a few minutes to start it back up.
Weber 48IDA main jet- 250 idle jet-70 pump jet-50

What is my problem here? I thought the main jet might be too big, but that would only effect 1/2 to wide open throttle, right?

HELP!!!!!!

 

On my racecar with a streeported 13b and 48IDA I have 225 main jets. It sounds like you are loading up the motor with too much gas.

 

Thats what I was thinking too, Don. But it only loads up when cruising, or off throttle completely. Wouldn't that be my idle circuit...not main???