I built a 350.......

350 .060 over, flat pistons 4 valve reliefs, 62cc heads, 2.02 1.6 valves, .495/.510 246/254 duration @ .050 hyd flat tappet, roller rockers, dual plane intake, 800 cfm. I'm using 1 light spring and 1 medium spring in the distributor set @ 40 degrees. I have richened the power mode, and power staging mode of my car, also set spark plug gaps to .045. When I'm accelerating hard it pops, feels like a mis-fire or maybe a back fire, I have a mallory coil flame thrower module. I have racked my heads on this for the last year, I haven't put more than 10 hours on it since I built it. Pop has been there, I'm out of ideas. My vac at idle is about 5 in hg and it's not too steady, but I heard that's due to the long duration of the cam. Please help.

The module may be breaking down under electrical pressure or there may be a loose wire somewhere in the distributor or one that is chafing against ground. Could be any of a dozen reasons. What I would do is to replace the distributor with a known good one, like take one off the motor of a good buddy or something and see if the motor acts the same way. That would eliminate the distributor as a cause. If the car runs better with the borrowed distributor, then get another one to replace the faulty one.

With the cam you have, you need at least 20 degrees of ignition timing at the crank, with 16 degrees in the weights, a total of 36 degrees centrifugal, all in by 2800 rpm's. If the motor is hard to crank with that much initial at the crank, interrupt the hot line to the coil and install a momentary push-off button that can be mounted on the dash or steering wheel. Press the button and turn the key to crank the motor. Once the crankshaft is spinning, release the button, allowing juice to the coil, and the motor will fire right off.

I really like an HEI for a street/strip motor. It's simple and bulletproof. Be careful buying a cheapo unit though. You get what you pay for. Here is one of the best in my opinion.
http://www.performancedistributors.com/gmssdui.htm
These guys will set it up for you custom-tailored to your application.

What make of carb?

Ok, so I leaned out the part throttle one step back, pushed my initial up to 22 and it ran good, still cranks too! Seems like I just needed more timing, oh it's a 1412 performer carb. I didn't clip the hood pins and I flipped my hood back! Man, I was pissed! Oh well, it was fun. I only got to try part throttle, it used to start pinging around 4000, so I swapped to the 1 light and 1 med spring, that puts me ay 42 degrees at 5500 rpm. I haven't been able to open it up since I put it in the s10 so I'm hoping for good results.

42 degrees is too much centrifugal advance for a 350. You're gonna hurt some parts. Drop it back to 20 at the crank and 16 on the weights like I suggested 2 hours ago.

look, I can't limit my cent. at 3500 rpm my spring combo brings in 14 degrees so with 22 initial. That's 36 degrees at 3500 rpm. Here's the kicker, at my redline... 5500 my weights will pull in 20 degrees. So with a base of 22, at 5500 rpm it will have a total timing of 42 degrees advance. That's because I am using a stock hei. I've only changed the coil and mod. I've changed the weights and springs