Difficult starting

[repairman]

I have a 964 C4 which has covered 150,000 KM’s and which is giving me grief?
Two years ago it would start and the engine would catch but then immediately die. Sometimes trying to repeat starting would result in a live engine, leaving it for between ½ to 3 hours would also work at times.
Eventually, it completely died. We live in the country and my mechanic is non-Porsche. It was in his workshop for a couple of months. He drained and cleaned the fuel tank, replaced the fuel pump, replaced air the flow sensor and idle valve (used), cleaned the crank angle sensor, cleaned injectors, cleaned all connectors, etc. I use 98 octane petrol.
All his actions got it up and running, a side effect as that the engine occasionally stalls on a trailing throttle but immediately starts again.
The latest is that on a completely cold start (left overnight) it will start but not pick up and dies. On the second start it fires up but when really cold is lumpy and will not respond to the accelerator for the first few seconds. Then for the rest of the day it starts without hesitation.
I am hoping that someone can point the finger at where the problem may lie?

[RedCoupe]

You didn't mention any work on the ignition system. Because your mechanic did so much work on the FI system, I would go over the ignition system thoroughly. Check the resistance of all ignition and coil wires, making sure that all the terminals are good. Look for cracks or worn terminals in the distributor caps, and if they have any wear at all I would replace them and the rotors. While you're in the distributors, I would ensure that the distributor belt is good. The spark plugs should be replaced unless they're nearly new. In any event, check the gap of the plugs. Make sure that they're the appropriate plugs for the 3.6. I would also check the ignition coils, as weak coils can cause poor running. I have compared coil resistance against new coils, but unless you have access to new, identical coils, bench checking coils is difficult. Other things that come to mind are fuel pressure, valve adjustment, and the head temperature sensor. Obviously, the fuel pressure can be checked while running, and the CHT sensor can be check with an ohm meter without removing it. You might also check the continuity of the idle and WOT switches on the throttle bell crank. Also, cleaning DME relay contacts might not hurt either. There are other things to check and verify, but that's what comes to mind right now.