What about an uprated fuel pump? Vac lines? Breather set up? Oil feeds oil returns? Turbo lines? Temp sensors? Gaskets?

Personally I wouldn't bother with the trouble of boring to 2.1. I just think you'll struggle, seriously with a silvertop going 400

Ask Karlos about parts required for th st170 route. Your more than likely gonna end up going that way in all fairness. And for a lot less money I'd think about settling for 300. But I'm all for people trying so give it ago. Only person that's gonna stop you is yourself