? about 4 cat system
 

Have heard from a few sources that the first set of cats or per cats are basically a resonator. My question is if i cut those out, welded up w/ straight pipe and left rear in place would it throw cel?

its gunna be 50/50 on if you get a CEL or not.

Thanks. Has anyone seen a cut away of a factory pre cat? Does it have any honeycomb material or is it strictly just a resonator?

BTW its a 99 4.6l romeo

Yes it does have honeycomb inside. It is a Catalytic converter and ,i believe, does everything a Cat is suppose to do.

I have a 04 and I cut my rear ones out no lights came on. Sounds way better too

'97 / '03 are very different than the 2004/2005 4 cat systems. '04/'05 rear O2s only monitor the front cats. The rears are not monitored for efficiency. Therefore, no CEL. As stated, it is a 50/50 chance a '97/'03 will throw a CEL and require O2 sims or tuning.

Has anyone who cut the rear cats off noticed any power gain?

It is a gain that only a dyno could recognize, and probably only noticed at high rpm. Otherwise, this is only worth doing to gain 15% - 20% more volume.