Brian on the s/c car I have the stock FPR modified (crushed, pulled back many times
)
I also have the Vortech RRFPR. If I were you (and I will be doing the same shortly) I would buy the kit for the vortech that has the different ratio springs. When I do my next change to the s/c car (lil mule) I will be installing larger injectors again and running either a 1:1 or 2:1 spring in it.
the turbo car has an adjustable FPR with a 1:1 built into it. Not sure of the brand. I just used a bike pump to see what the rate was.
If I were you I wouldn't worry so much about the overboost of the mitsu turbo as these heads flow pretty well and I bet it doesn't creep too much on you. For now I would even use the internal wastegate to simplify things a bit. You can always port the flapper opening to relieve the exaust to slow it down some.