I have a series 2 in the s13. It's completely stock except for a few basic mods: godspeed FMIC kit, spec clutch disc, full 3 in exhaust (no cat), and walbro fuel pump. I put a manual boost controller that I got from ebay for $12 and set the boost to 10psi. It pulls hard sometimes and sometimes it doesn't. Tonight for instance, I down shifted to 3rd going 60mph on the highway to feel the pull, when it hit 6k rmp it started to back fire and sputtering then after that, it did not pull whatsoever. When I got home, I popped the hood and saw a glowing red turbo and the exhaust manifold. I am guessing it's running lean...
I know for a fact that it's got a dirty airfilter but i don't think it has anything to do with it. There is no vacuum leak or boost leak. It has the sparks plugs (platinum) for 300zx tt. I am going to check the gaps on them tomorrow, change the fuel filter as well as the airfilter. If neither works then I am going to have to look at the timing. Any suggestions will be appreciated.