Manta B GSI

Hello Have since Saturday finally a Manta B GSI. The car is from the car in a top condition. 86 model. Only the engine is still not running properly. After I have changed the glow plugs (probably in German wrong but you know for sure what I mean ), and the air filter changed, the engine runs quieter in the stand. Only the engine does not turn up. In stand already, but as soon as you drive, it runs at a certain speed to stutter. Have the distributor What can this be about ??? Would be happy if someone can help me. I also wanted to know what I have to consider when converting from 2L 8V to 16V, and whether the electronics have to be completely changed with (electronics … HAHA) Which engine can I take at all ? Only original manta motors ? Is there the GSI engine in several versions ? Thanks in advance