2003 Chevrolet Silverado 2500 HD Q&A

2003 Chevrolet Silverado 2500 HD Question: my engine loses 2-300 rpm when kicked in to passing gear.

I have replaced the rubber fuel lines. the check engine light came on but went off before I could read the codes. -
Answer 1
Codes are still there, unless you have removed the battery cables for some reason. Computer has a good memory! Turbo working? -
Answer 2
scan codes and post so we can adv -