I have a 1994 Ford F-150 Lightning. I removed factory exhaust & installed dual exhaust with 40 series flowmaster mufflers. I put in crossover tube & installed 02 sensor in crossover tube. Now the check engine is coming on. Pulled codes & it says that the EGR flow is low.

Does anybody have any ideas what this could be or experienced this problem?

If I'm at wrong forums, does someone know a link for the first generation Lightnings.

Thanx for your help & time.