[Johnny Danger]

Originally Posted by The Radium King

do the ebay headers and leave the stock mid-pipes/cats. that's how porsche does it in countries with less strict emmissions requirements.

north america has the added requirement for emmissions reduction at start-up, so american cars have an additional warming 'pre-cat' on the headers and a secondary air pump, as well as sensors and ecu programming that checks to make sure both are working. row does not have this requirement, so row cars do not have cats on the headers or secondary air pumps, and no sensors to confirm their operation.

you can get catless, equal length, stainless headers on ebay for $65; the cheapest you can get new catless midpipes is $500. get headers without cats, however, and you have to deal with the sensor that is there to confirm the operation of the now-absent cats (or you get a 'check engine light'). you can reporgram your ecu to row, you can buy 'foolers' (fvd sells them) or you can make your own. all the sensor does is look for 02 content in the exhaust. it can be fooled into thinking that the cat is working by distancing it from the exhaust; some guys just hang it under the car, or you can get spark plug savers that thread into the exhaust bung and get the sensor out of direct exhaust flow (make sure your new, catless headers have two bungs each). there is also supposed to be a trick that uses a resistor or diode wired into the sensor; google is your ally for cheap, easy solutions to this.

other considerations are pipe diameter; oem for a 3.2 is 1.25" into 1.75" (ebay headers vary, but 1.5" into 2" is typical); go much bigger than this (or go completely catless or to a high-flow muffler) and you get into backpressure issues. reduced back pressure is good at high rpm when the engine is trying to flow as much air as possible, but at low to mid-range some back pressure is necessary to facilitate combustion chamber scouring and make max power. i've yet to see a dyno of just a high flow exhaust that does not indicate a drop in hp/torque at lower rpms. that's why most dynos from tuners include ecu flashes to compensate or don't start until 3000 rpm to hide this fact.

other things i've read is that cats tend to kill high frequencies, so a catless exhaust can be ricey sounding. also, i've read that those who have compared row to us spec cars have found the row to only be several hp stronger, so better figger out what your $/hp threshold is. i can justify $65 for several hp; uncertain if i can justify $500 for the same gain.

ps - lobo; what's the word on the wrap - worth it? keeping things cooler at all?

With all due respect, at 600 cells the secondary cats are arguable the most restrictive (and possible the heaviest) part of the oem system . Therefore, if one is going to leave most of the system intact, it would be far better to leave the headers/pre-cats in place and remove and bypass the secondaries .