Noone yet has given me a tenable reason why you can't run a turbo on a 914.
However most people seem to be agreed that you cannot run more than about 12-14 pounds of boost.
It does involve a lot of work to get everything to fit right. I made an attempt to get a turbo into the area either side of the transaxle, taking exaust from behind the heat exchangers. This is bad juju. You want the exhaust hot - while it is hot, it is expanded, which pushes the turbo round better. Another problem with this area is you end up with the turbo dangerously close to the bottom of thesump which means you nead a scavenger pump to get oil back to the engine.
If you are serious, I would add an external oil cooler, since the turbo is going to warm the oil up some.
http://not2fast.wryday.com/turbo/glossary/...urbo_calc.shtml is a turbo calculator - using a 2 litre motor it suggests that an output of around 150HP might be possible. Using a 1.8 motor with 96mm P&Cs, you might get 140.
Note that these figures also require intercooling, and are based on 65% volumetric efficience @ 6100 rpm - which ain't likely with a type IV - although Jake Raby might have a better idea on that.
Simply fitting all this stuff in is hard - there actually isn't all that much space to add stuff in a stock 914 engine bay.
I ran all the numbers - made a half assed attempt, and gave up. I might try and get it going once I am done getting the car running on the new Subaru motor. If you really want HP - I would do either a 6, a V8, or a Subaru Motor.
Fiid.