i was wondering about hi-flo cats. how expensive, where to find, how much better then OEM cat. any answers greatly appreciated

Im not sure if any one is better then another but here u go, seems like a good price.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2400434436&category=6771

they free up some hp, make your car a little louder, etc. i have an muffler and plan on getting a CAI, header, and hi flow cat to compliment it. then ill be nice and loud and have an extra kick. but really you only need it if you dont plan to be pushing stock hp and if you are redoing everything else to do with it (header,muffler). ebay has several from Bom Racing too that are really good and are around $50. thats what im ordering.

is there any difference between 420a cat and 4g63 cat?

i have a test pipe (race pipe) on my car.. it was way cheaper..but i will have to put my orig. cat back on when its time for emissions in 2 yrs..lol.. u could always go that route .. just a thought.. if you wanna check it out try

http://www.mufflertech.com

he sells the test pipes as well as high flow cats..

but they will make your car sound a bit "ricey"...but it is supposed to add bout 15-20 hp on NAs and bout 30-35 hp on forced air.. just thought i'd give you another option to look into=)

15-20 hp seems a bit steep imo...

I was thinking more along the lines of 3-5 at the wheels, depending on the supporting mods

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Black 96 ESI 5 speed
few mods here and there

yea, there is no way you gain 15-20 horses. i have one on my car and its a lil louder than stock. you sacrifice some low end power, but you get it back in the top end. it helps everytihng really kick in about 3 grand. im sorta pleased with it. i dont like that i lost that much needed low end power, but the high end is pretty awesome. they say its pretty much a waste for us n/t guys, but thats wat they say about headers too. turbo guys benefit from this the most. 4g63 cats just have a bigger diamater piping than the 420a ones..the only difference.