How to make your own test pipe aka straight pipe.

Take note that this is illegal, I take no responsibility for you failing emissions.

Tools/parts needed:
19mm socket/wrench
PB blaster
Torch
Impact gun
Ratchet
Tape measure
Die grinder
Cut off wheel or sawzall
Welder
Whatever size pipe you want to use
Flanges
Gaskets


Ok, to begin, I made a test pipe for my FACTORY exhaust. My way is going to be different than yours if you have an aftermarket exhaust, being all the different designs of exhausts. It is pretty much is the same concept either way.

First you're going to have to unbolt your catalytic converter. The bolts are going to be a pain to get off, so make sure you soak the bolts in pb blaster and heat them with a torch if necessary.

After you have the cat unbolted, measure from flange to flange, then from in between each flange. I came up with a total length of 16 inches from flange to flange and 15.5 in between flanges.

I chose to cut the flanges off the cat to save some money, as stated before if you have an aftermarket exhaust, you can skip this part. I put the cat in a vise and cut the flanges off with a sawzall. I then had to drill out 2 broken studs in one of the flanges. After the holes were drilled, I cleaned the flange up with a die grinder.

Once you have your flanges, measure your test pipe. I measured to 15.5 inches, and cut the pipe with a cut off wheel as straight as I could. You have to measure your flanges if you have not used the stock flanges, and compensate the measurement of the pipe to have a final size of what you measured from the cats flange to flange.

Take your welder out and set one of the flanges on a flat surface, and line up the pipe as best you could to the inner diameter of the flange. Spot weld the pipe to the flange, and check to make sure the flange and pipe are aligned properly. If so, finish welding the pipe to the flange.

Next your going to have to line up your next flange as best as you can so the flanges are parallel. you don't want to have one crooked, because you'll have to redo it. Spot weld, check, finish weld. Check both flanges for pinholes in the weld, if there are, close them.

If you don't care about welds getting rusty, you're done. I chose to use vht flameproof spray paint to protect the welds from rusting/rotting. I painted the whole pipe. Let dry, and install.