Hate to guess $$ , I would TRY to keep the original block in that car at all cost if it were me. When I did service calls in my working days I would joke; if you have a Mercedes you better put in the neighbors yard because the price will double/triple.
if you have tried to mount it and it won't sit flush then YES you need shorter studs but mine extended past the spacer as well but the wheel will mount flush.
I wouldn't jump either, I would wait to see what your mechanic says about the injector, could be the coil, it's a waiting game till then. The computer is pretty durable, computers don’t go bad as much as you would think.
the wheel will allow a little space, install the spacer with two nuts then see if the wheel will fit flush. If they will install the rest of the studs then the wheel.