Just fired up the rebuilt 350 (now 355) last thursday. She started right up but didn't idle very well but improved when we adjusted the timing with a timing light. So we went ahead and started the break-in procedure (2000-2500rpm for 20 minutes). She ran great at that rpm but would sputter and almost die when you let off the gas and didn't idle very smooth. I took her for a drive around the neighborhood and she lacked power and would again sputter when I let off the gas. We noticed that the injectors looked like they weren't spraying correctly (the mist looked a little drippy) but other than that, everything was fine. The only other thing we could think of is that we might have a vacuum leak somewhere. The gas in the tank is at least 2 months old, could that be the culprit? The only things that aren't brand new on this engine are the throttle body, plug wires, and distributor cap and rotor. Everything else is brand new. I'll try running some B-12 through the gas tank and check over the vac lines again for now. Any suggestions as to what might be wrong?