i got an uppipe on my wrx, but now the check engine light comes on.is there a brand of uppipe that works with out turning on the check engine light?

 

The stock uppipe has a EGT Sensor in it. If you bought an uppipe without an EGT sensor bung, and imply unplugged the sensor, that could be the cause for your CEL.

You need a 2.2k ohm (not 100% sure on the value) resistor in place of the sensor to get rid of the light.