my 93 r-1 has 40k miles on it..its my second rx..just got it last week..had typical no boost on the second turbo..i did the silicon hose fix...now the car makes boost on the second turbo but backfires while coming on boost sometimes it backfires between 5-10 lbs and sometimes not til it hits around 11-12...also car idles kind of rough...cleans up with higher rpm..also appears to run very rich..lot of sooty black smoke...any advice appreciated..mike

 

A puff of black/brown smoke usually means the car isn't burning all of the fuel going in. Sounds like the car probably just needs a tune-up.

While looking to buy my RX I recently went over a 93 w/ backfire probs, and Dave @ KDR told me that those issues are usually easily tuned out/nothing to worry over.
GL.