[Schulisco]

Hi,

I have to admit that I'm not in the MFI and F-model field - but I also struggled heavily in the past with back firing, poor and below 40°F impossible cold start (ok, not here) and poor power delivery together with a heavy fuel consumption on my '81 SC.

What I figured out - the Porsche engines live and die with the mixture! Especially the fuel injected engines.

Either too lean or too rich produces several of your experienced symptoms as well! Guessing you're experiencing a high fuel consumption as well (for sure the carbs itself aren't that fuel efficient) of 11mpg or less, right?

If you haven't modified anything on the engine there must be sth wrong. Either air leaks or more likely misadjusted injection and mixture. Did you checked the fuel pressure? Probably it leans up while reving high due to dying fuel pump?

To verify the mixture I recommend to make tests drives with a lambda tool applied (e.g. innovate LM2) while driving with several loads at several temperatures and speeds on the road or even better on a dyno!
Best for performance of an aircooled engine is 0,85 lambda / 12,5 AFR on WOT, not more and not less! Also around 1 / 14,7 on idling and cruising with 30% throttle...

Regards, Thomas