Power loss shortly after start

Hello, fellow sufferers!

Got a little problem with my fat guy again.

If I start my 4.2 ABH early or whenever (mainly in cold condition, but sometimes already in warm condition) it runs bad for the first 2-3 minutes (sometimes immediately). In idle and with inserted driving stage everything is still OK. As soon as I'm just gasping, it's like swallowing himself for a short moment. I must then also use the accelerator more forcefully in order to be able to drive at step speed than if it is running normally. If I turn off the car and it's warm and it's back on after 5 minutes, it's like a bee. Without any problems, already on the first MM takes the gas clean, has full power.

I have the FOX-Racingsystem (MSD-replacement tube and ESD) underneath. He's usually pretty grumpy. But if the problem occurs, it gets really loud.

I checked KATS and the stakes are fixed and not added. Candles are new, distributor fingers are new, Lambda new, air filters new, gear oil is changed and perfect from the stand.

I'm baffled... Sometimes it only starts after 2-3min and sometimes right after the start. If he then runs like that, then you can really hear this wave-like acceleration, which, however, if he is not running perfectly there.

Error memory is empty and otherwise there is no hint. I am at a loss and hope that one of you already had this problem. you have a lot of clues where it could clamp?!?!

Thank you!