so i recently bought a 91 pickup with 213k miles and plan to do an sas/doubler etc. doesnt really matter. the guy had a terrible exhaust on it. pacesetter pos. had the worst leak. sounded like lifters tapping.

anyways i got a brand new LC Engineering street header and put it on. then took it to an exhaust shop to have them weld it all up and install a basic flowmaster exhaust. runs amazing now and its nice and quiet. but now im getting a check engine light. did the jumper trick and got engine code 71. (EGR system)

any suggestions on what to check?

 

Make sure there is good exhaust gas flow back to the EGR valve. Gas is redirected back from the small round ports above the exhaust ports. I found on my LC header I had to issues. One was the weld bead where the round exhaust tube was welded to the flange blocked off some flow inside the header flange. A Dremel and small grinding bit flattened off and rounded over the bead in the area between the main port and EGR port. Then the web of the gasket between those two ports was in the way, so carefully trimmed that web away on the 4 ports , so instead of (o O) you get (oO) with the section between cut out, and now it works much better:
https://www.4crawler.com/4x4/CheapTr...ndex.shtml#EGR