Porsche Repair: 1977 Targa 3.0 backfiring, BTM motorwerks, backfire 911

Question
Hi Brad,

recently I have bought Targa 1977 3.0 in overall I believe reasonable shape. Two things I would like to ask about are:
1. the car usually starts normally at the first time. however, when I drive it and then switch off the engine, and then want to start again shortly after - 30 min or so - it would take 4-5 attempts to start. If it is few hours and engine cools down, starts imemdiately again. I drive it every day. It never happened that it would not start at all.
2. Clutch and gearbox work well, though when driving with let's say second or third gear but no power added via foot, it does small backfiring. When accelerating backfire goes. When idle, engine nicely sounds with stable 1.000 or so.

Would you have any ideas please? Otherwise lovely car, so far reliable.

Thanks & nice day,

Norbert

Answer
Norbert;

First, your car's engine must have been swapped out with a later engine. Your car came with a 2.7L engine.

What year engine do you have?
Does it have a O2 Sensor?

You probably have a issue with the fuel management. Doed it backfire through the intake or exhaust.

Brad