I bought a built 99 all motor busa a few years ago and the for the past year its been running rich. At first it just took a little extra throttle to start but now it needs to be wide open and needs the idle adjuster to be on just to idle when its hot. I noticed the plugs were fouled (all evenly) so i did what every back yard mechanic would do, start throwing parts at it. After a new air temp sensor, boost sensor, coils, set of plugs and all the connections checked I'm fresh out of ideas. the only other things i can think of is the bosch 280160237 fuel reg thats on it but its in the return line. When a fuel reg goes bad it lets more fuel in right? Which would mean the fuel pressure in the rail would be dropping not increasing. If I'm wrong let me know. I would have bought a new one but it seems to be discontinued and i cant fine any other fuel regs with no return and a boost port that goes up to 44psi/3bar to try. The only other thing i can think of is maybe the tune? It has a power commander v thats been dynoed. It ran and idled mint when i bought it which is why i never thought it could be the tune but idk where else to look. If any of you guys have any insight id be pretty excited about it, thanks.