\'72 K5 - Bogging down on accelleration/backfire through carb '72 K5. 350, v-8 short block. Over 150k, smokes some on start up. Idles fine, even when reved at high RPMs. Will idle for extended period of time. However, when under load (ie in gear), it boggs down (when accellerate it acts like its flooded) with sporatic popping/backfire out of driver's side of carb's air intake. I've been told that it could be a loose timing chain, a stuck valve, the fuel injection pump in carb, or an out of balance distributor. Any ideas on potential source(s) of the problem and/or diagnostic tips or tricks would be appreciated.