Hi Robp,
I also have a 1987 K100 Turbo, unfortunately it is not the same exact turbo kit, I have the split intercooler, it appears you have the first generation and because of that, I cannot guarantee my knowledge of my motorcycle carries over to you. The turbo on my bike is a IHI RHB52, the specific turbo code is a VC19, so if you can find a turbo shop who services IHI turbos that would be ideal. I think your turbo is an ihi as well, but i dont know if it is a rhb52 vc19. my turbo just siezed and i am in desperate need of a compressor wheel and intake impellor, if you find a good turbo shop, please reply to this thread. also, as turbo is expensive, i would make sure it is not a piston ring issue and not a turbo bushing.