My cel has been on for a few months and i just got it read again and found out it's the evap control solenoid, my guess is this is what recycles gas vapors or something? i dont know, but how can i fix this, and where is it?

Nos Fogger Kit,AemCAI, TopFuel UDP, pacesetter cat-back, ARD bored 57mm t.b., P&P intake mani, Ractive front/rear strut bars,rear tie bar,eibach sportlines,tokico blues, morosso wires, ngkIX plugs, konig subzeros,proj. heads,gunmetal tails, rev.indiglow gauges,reverse light mod