BPT Valve for 94Q45

[Ted]

This morning when I start the car, the engine at idel shakes a little bit. When I start to drive, the engine light lite up and the engine is rough. I recently have a mechanic changed the O2 sensors, and the EGR valve within the last 3 months. The car was running very smoothly until now. I hear a little knocking when I listen to the engine. When I pull the hose under the BPT valve and block it, the knocking noise decrease. Could it be the BPT valve? Or is the O2 acting up again?

Please advise.

Thank you.

TED