I have a 2001 s4 6 speed with stage 2 GIAC, Borla exhaust, 710n diverter valves, new o2 sensors, and new MAF. My issue is Im not boosting in first gear at all and its sluggish in 2nd and 3rd (it takes longer than it used to to peak at 20 psi). Does anyone have any ideas as to what my problem might be? I also put in new spark plugs and throttle body boot.

 

You mentioned throttle body boot...

I don't know if you are referring to the seal but if you replaced a seal perhaps your boost is escaping through a failed seal, or an improperly seated seal. Just a guess.