Most aftermarket turbo set-ups, on any car,
used to be suck through. The idea was that the carby still worked in a traditional sense in that the air (just more of it) was being drawn through the carby.
There are only two real reasons why the preferred option now is blow over suck.
1 is that you can use an intercooler. You cannot use an intercooler on suck through as it becomes an explosive device in case of a backfire, remember its full of hot/compressed fuel/air mixture, not good. Note, you don't need an intercooler with some fuels such as methanol, but this is not really a street car option
2. On suck through the turbo is under vacuum during idling and low loads. More particularly when the engine is at high speed and the throttle is suddenly closed such as a gear change, this tends to suck oil into the air/fuel mixture from the turbo which increases the chance of knock. Modern turbo's are better than older types but it's still a consideration
Obviously there are more complicated issues that we could discuss such as evaporated fuel displacing air (reducing potential power) and blah blah, but suck through has been proven to provide good results. There are plenty of working examples out there, the original Zakspeed turbo mini (QIK850) was a suck through and I'm pretty sure Wayne W's Mk11 is suck through as well. The first rotary's to break into the 9's in Australia were all suck through....
In saying all that
I would try to use the turbo metro set-up (or at least the parts) for a conversion knowing that there are limited people who can help out should you have any problems. This is a blow through and will allow you to add an intercooler to the conversion without adding to much cost.
Regards
Daniel
