As for my problem.
SES lights on when I decelerate only. It happans couple of days after I've replaced supercharger by Paxton rebuild one. There are no problems with driving at all like bad driving, shifting, nothing. Only SES from time to time. Our services seems not to be happy to see the code appearing from time to time. So I hope together we will manage to fix a problem.
Good withes from Russia!
Vitaly

Also my dealer from USA told me that there is no Boost control selenoid on this car besides supercharger by-pass valve. Is he right?

Hey, it'* great to have you here. Even better with someone from Russia! Amazing that you have the US car hobby. Must be difficult at times.

Your dealer is right. There is a bypass valve (or wastegate vacuum valve). It only costs about $20 US. Are you sure all the vacuum lines are connected?

The part number for the valve is 12353309 and costs $12.98 US.
In case you need to replace the harness for the valve and FPR, the part number for it is 24502303 and it costs $8.46 US.

These prices are from www.gmpartsdirect.com and don't include shipping cost or a rubles conversion! Hope this information helps. Your valve could be sticking, or you could have a vacuum leak. Fuddyduddy may have more to add here, or may correct me.