I usually work on my 2002 GS300 myself, but a while ago I had an independent mechanic change out the leaking valve cover gaskets. While at it, I had him change the plugs as well. When back together it had a small miss and I called him back to investigate. He said it seemed like a vacuum leak, but was never able to fix it. I let it go and eventually the CEL came on. I want to fix it myself and have been putting it off. Now I'm ready. It's been running progressively worse (rough) at idle and has developed a serious hesitation on fast acceleration from stop, as though it's flooding. I'm getting black soot accumulating in the tailpipe. Also the tranny hesitates shifting from gear to gear especially at start-up from a dead stop, but only if I accelerate rapidly.

I had the codes read and they are 61, 62, 63, and 64. Wondering if the VSV ( Failed Vent Solenoid code 61) at the engine compartment could be the culprit, or if it may be related to the way the mechanic put back the wiring (those nasty breakable little plastic clips), or if he screwed something else up while working on it. I didn't care for the way he started the car after finishing his work. He gunned the engine immediately to blow it out. Based on my problems now I am wondering what effect that had on any of the components in the EVAP system. I want to get into it, but want to have all possible parts on hand before I do.

Any ideas from you folks on where to begin looking would be appreciated.
Thanks in advance.