not sure, but i think i've seen some fbody guys pick up like 10-20 hp from a single cut out or so they say.

 

i really have to question the whole loss of low end power from "too little" back presure, i have heard that for ever and kind of think it might just be a perception issue, could it be that it is just soo much louder that your not pushing the pedal as hard.

i have installed quiet mufflers before and the truck felt faster, just because i could completely floor it and not make alot of fuss and run hard.

here is a closed vs open chart from my truck



and here is a chart that shows the actual hp diference of the chart above



you can see from the beging to the end the hp is up, i admit i have the stock restrictive exhaust and not a free flowing cat back but i bet the results would be similar, just not as extreme.

 

If you have the cutouts in front of the cats, you may or may not throw a code, the codes will be something about the rear 02 sensors and can be ignored. They are used for emissions testing and catalytic temperatures. If you do get a light, you can get it checked at AutoZone and have them clear the code.

I have run around on open header for a weekend and didn't throw a code. I have also thrown one on the first WOT run I made after uncorking them too. It just happens sometimes. Either way, you don't need o2 simms. From a performance standpoint you will get better results from putting them in front of the cats, but there isn't much room and it's a tight fit. You may not get as good of a 1/8mile time, but you will probably trap higher speeds due to the less backpressure giving you increased horsepower but reduced torque. It's a trade off some are willing to go with.

If this tells you anything, I always unbolt and remove my exhaust from the y-pipe back when I go to the track.

 

Good info, guys.

PARISH - is that dyno sheet from a cutout before the cats?

 

that is pulling the exhaust at the y, so after, i would expect to see another +5hp/tq if it was before.

my next trip to the dyno will have no cats and a single 3" electric cut out.

 

Not the case for me, I assure you. With the headers uncorked, like they are now, I think about warning the peo-ple next to me if they are old and/or ladies, but then I think .... naah .. oh well. The pedal will only go so far though ... WOT is WOT.

 

I'm leaning towards the 'before cat' position since I just found out my new HPP3 can check and clear DTC's. Anyone got any pics or info on their before-cat cutouts? Will the dealer balk at any warranty work if the cutout is just installed and not open?