Got the SES twice today, both on half throttle acceleration up a slight grade. Checked it on the Scantool, says 57 - Boost Control Malfunction. I am guessing the BCS is failing? It came on twice, both about 5 seconds each, went off about 2 seconds after I let off the gas. Let me know. Thanks!

did you visually check the BCA to make sure it is moving correctly? how about bypassing the BCS

Sounds right. You'll be happy to know the BCS is cheap and easy to replace.

Does your boost seem to act normal?

It does act normal, I got full boost, and I got proper movement when revving at idle. I DID notice around when the SES came on, the whine made a fluttering type sound.

Yeah, BCS.

Sounds like what happened to my '92. When my BCS failed, boost was normal but the SES light came on when letting off the accelerator at around 40 MPH or so. The BCS only takes 5 minutes to replace - 1 vacuum hose, 1 electrical connector, and 1 bolt.

I don't want to hijack but what if you replaced the BCS with a brand new one and tried another BCA and still get the code once in a while? What is left?