Have trouble with my construction site again

ALso, a few infos in advance:
Last month everything started with the already described wavelike acceleration. In addition, the small about 35 ltr has drunk on 100 km. Then I changed Lambda and temperature control, also a hose for engine ventilation.
Unfortunately it had somehow shot the starter, which is now also new. ^^^
Consumption is now back in the frame, but it's ticking at idle. The speed drops to 0 in a second and goes straight up again, to about 900 where it should go. Sometimes he goes out, sometimes he doesn't. However, it consumes quite a bit of fuel again (logically when it always drinks off I think) and it also smells extremely like a gas station in the interior.
Who's got an idea? Before I spend 2 weeks inside the workshop again and have to pay 1000 euros

Thanks and a nice weekend!
- sonst haste im Zweifelsfall 3 Fehler drin die es aber nicht gibt.