Redline in the 2.5 RS is about 6400 (I don't know exactly, I'll have to look when I drive home), but accelleration drops off a bit over 6000.
I have seen a 99 2.5 RS with a Japanese 22B engine in it. I don't know how much it costs, but it is possible, and it adds a lot of power.
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2004 Subaru Impreza WRX STI (daily driver)
1999 Mazda Miata (track car, slow, but finished the SCCA Runoffs)
1987 Porsche 944 (being rebuilt)
