Help for a ’95

Hello, I’m new here and I’ve tried it before. Probably the topic MKL has already run ten times. Nevertheless, I would like to hear your opinion. I ripped an Omega out of the scrap metal a few days ago, because I thought it was too bad for the scrapping premium. It’s a 2,0/15hp CD Built 04/95 engine is probably an X20SE. He has 104 Tkm on the clock, and the retiree who drove it was rather nice to him. ;-)) You can’t scrap something like that. ;-)) So I did it. But now the MKL is blinking, and the local FOH thinks that he can’t help, because his PC doesn’t find a mistake. But it’s the case that the engine doesn’t take any gas under 2000 rpm, and only runs again at 3000 rpm. However, the idle is quiet at about 700 rpm. But the fuel consumption is really too high at 16l/100 km. So what can I do? Lima was new. Would I be happy if I got help there, because I don’t give it to the scraphead any more. Greetings to all Oms. i- Fans Arne