Check Engine Light - error code T0340, Camshaft Position Sensor Blank 1

the exhaust has nothing to do with this unless they hit a wire going to the sensor or the sensor itself installing the exhaust but the sensors should be on the front of the engine one on each head to monitor the camshaft positions. gm's seem to be common to throw these codes ( my envoy and Suzuki xl7 did similar things) get it checked at the dealer they can scan it and monitor data to see if the cams are in sync with the crank. If it's intermittent may be debris on the cam where the sensor reads the position or the sensor itself. do an engine flush if it keeps doing it then replace the bank 1 sensor and if it keeps doing it further diagnosis may be needed.