Help! Poor acceleration and backfiring

[jkmc17]

I have an 1982 911 3.0L. After initial start, I would start to accelerate and the car would have a small stutter and backfire that I could feel through the accelerator. I decided to give it a tune-up, not knowing when the last time it was done. I replaced the:

Sparkplugs and wires
Distributor cap and rotor
Adjusted the valves
Set the timing
Replaced some vacuum lines
And recently had the fuel pump replaced.

The problem still exists and is more evident when the engine is cold. Could this be a sensor problem? Please help. This is getting very frustrating.

[mfiazzo]

you may want to check the CIS system for proper adjustment