The walbro 255 will pump more than you are shooting for.
what CC are the stock injectors? What Bar is the stock FPR?
I am not a saab speciallist but I know guys that are. I will talk to Darryl tonight and shoot the shit about your car and see what he thinks. PM, FastTwins on here, thats darryl owner of Albany Speed Shop. To talk prices on the manifold and down pipe.
If the manifold is anything like the stock one I just coated for someone, there is enough realstate on that flange surface to cut it off and convert it to a t3 I think. Or the cheaper route, but would still work just fine, would be we make a T25 to T3 adapter flange. Put studs in the stock manifold, and tap the T3 flange on the adapter. make it easy to install, might raise the turbine off the manifold 1.5" or 2", so the down pipe would only need a small section welded back in place and a new flange welded on to mate to the bew turbo.
Making an entire manifold would be the best solution, turbo placement would be right were you need it to mate to the DP, flow the best and fit the best… and of course cost the most.
If the stock bottom end can take 300whp, wick the boost down on the new turbo and tune it for that. Whats the weak points on the motor?? rods? ringlands? crank? Keeping timing safe, and running just enough boost with the proper AFR to get you around 275-280whp would be easy on a 28RS, and give you head room when you build the bottom end.
That turbo on 1.8t VW’s, what I pretend to know the most about :tongue, make solid 260-320whp with less displacemnt. and see spool times around what you saab guys see now… but they can still pump air up top where the little stock saab turbos fall off.