Need Carb tuning 101 class

Sounds like you've pretty much ruled out ignition timing as the problem, in other words, all signs point to carb issues. I would bet that upping the accel pump shot would cure the problem. If the Edelbrock users here can point you in the right direction, fine, you'll save the money of having to buy an entire new carb, regardless of brand. Also, I set my timing a bit differently than just setting the intial timing and calling it good. I feel that total advance, working together with the right advance curve is the best way to make sure your timing is right. To do that, I use a dial-back timing light, and set the dial for the total advance I want. For instance, my Mustang uses 36 degrees of timing and I like to have it all in by about 2800rpms. So with my light set at 36 degrees, and the engine running as close to 2800 rpms as I can, I adjust the distributer so the timing mark is at "0" with the dial adjusted. Then let the engine return to idle and set the idle speed on the carb. Once that's done, check your initial advance, mine was around 9 degrees, which is not enough for a non-vaccuum advance distributer. To fix it, I swapped to lighter advance springs in the distributer, fired it up, and rechecked it, and found it to be the 12 degrees I wanted at idle. This is not the last word in timing, and LOTS of people just advance it until it pings under load, then back it off a tad and this works very well in most cases, but I've always liked to KNOW what my total advance is without "hoping" it's right. Besides, my car is so loud inside compared to my Mazda that I'm not sure I could hear it pinging until it was too late.