[WFBowen]

Rich: My advice (keep in mind that I owned a 912E in Calif.) is to hang on to any and all smog parts - you never know when your state will adopt the Calif. procedures/standards. Two reasons for taking off the thermals are 1. The exhaust stream flows much better and 2. The cyl. heads drop in temp. which should help with longer top-end life. As for rebuilds, I think that any shop that does a good job with TypeIV motors can rebuild your engine, but make sure they do the heads properly (i.e. quality guides, machine work, etc.) as the heads are the weak link on these motors and are very expensive to replace. Also, if you're running without an EGR pipe, I'd double check to make sure the EGR passage to the intake is blocked, as you don't want to lean the mixture with fresh air under EGR-open conditions.
Good luck,
Bill.