I just put on a set of Gibson headers and a Magnaflow #15749 on my 1998 F 150 while doing the work on the exaust I came to be wondering how resterctive are the factory cats on these trucks? are they worth replacing with aftermarket high flow ones and if so, do you out 2 or 4 on?

 

Yes, it would be worth it. Only put 2 on.

 

upgrading the cats are supplementary upgrades, meaning if theres a need for the extra flow, the upgrade would justify it. Just dont expect a huge gain from it.