930gt-40r, the Proto setup works great and is a simple and cheap solution for aftermarket turbocharging a naturally aspirated engine. Otherwise you're up for serious $$$$ for aftermarket standalone EFI.
I only run the Proto Stage 3 CHIP and dual rate fuel pressure regulator on my existing setup, but eventually I will swap out my OEM ECU for the Proto Motronic MAP Sensing ECU, which is a more refined solution and still cheaper than an aftermarket Motec/Autronic setup. Just drops in place of the OEM ECU, uses existing loom and just requires a vacuum line run and a IAT & TPS sensor mounted to the throttle body.
For the 993's, Proto has a variety of TT conversions/kits, so get in contact with them. I'd say you can single turbo a 993, but lumbing might be easier with the twin setup, because of the twin distributor in the path of charge air pipe in a single turbo setup. Speak to Todd Knighton.
'89 911 Turbo Cab
Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition