Cat Replacement - Magnaflow Stainless or Race?

[kommissar]

My stock cat is completely shit inside and needs to be replaced. I'd rather buy a high flow cat than just run without one and have to pay off a mechanic so I can pass my emissions inspection every 2 years.

I am looking at the catalytic converts on this page and would like to get the oval shape because it best fits under the e30. My question is, what the hell is the air tube for? Does it need to be hooked up to anything or does it just hang out there?

Also, what is the size of the stock piping, is it 2"? The reason I ask is because I'm going to need to buy some Y-adapters to go from dual piping to the single 2.5" oval and then back out to the dual piping again. What is a good site to buy this from?

Finally, Magnaflow now makes "race" catalytic converters for about $100 more than the stainless one above (see here). I don't really think that this is worth the extra $100 considering their cats are already high-flow. Anyone think differently?

[browntown]

they sell them with air tubes and without, some with o2 bungs some without. Dont know what the airtube is for, but if your car didnt originally have one, screw it, you prob dont need one.

Run the application guide for an 87 325is, and it lists 23554 direct fit and 94007 universal. I'd say go with one of those.

http://www.car-sound.com/02product/shopdisplayproducts.asp?portal=49state&SID=4BMW&id=121&cat=325iS

[kommissar]

Thanks

Wow, I didn't even see that feature on their website.

They got it almost-correct. The Triflo on my car is aftermarket, but I think even the stock exhaust had dual piping all the way back, which would make the correct cat the 94008 with dual 2" inlet and outlet.

Thanks for the help.

[turboconvert]

hytech headers has some pretty high quality cats.. from what i hear they flow really good and do a better job than most factory cats...