i just got and installed my new flowmaster american thunder (3" intermediate pipe, and 3"tailpipes) before i installed the system i was kind of worried on getting the intermediate pipe to the cat since the flange is different on my car (mines an 85 and the systems for a 86-91) butttt.... it all worked out quite nicely, i cut the flare off of the I-pipe and got a piece of 3" pipe flared to go over it in place of the cat and made a flange with the same bolt patter as my Y-pipe flange out of 3/8" steel and used a hole saw to cut the 3" hole in it and welded the new "Cat" to the flange, then bolted it to the Y-pipe, with 4 high temp-high grade 3/8 bolts and lock washers.... everything is working great so far...no leaks or anything, i also am pleased with the sound/tone, its decently loud, and has a real nice tone under acceleration...seems to flow alot better being 3" from the Y-pipe back and no more cat.

all u guys out there who dont like flowmaster...u r are welcome to ur own opinion, but i think this exhaust is SWEET!

 

good to hear. I'm happy with mine too.

 

i wanted the American thunder but couldn't afford it. I just put on the 80's series muffler. It isen't as loud as i hoped it would be. Oh well, you pay for less, you get less. Is there a "Break in period" for the flowmasters?

 

Seeing as flowmasters work on baffles and not glasspacks i really dont think they 'break in'.

5litre, do you have headers or anything ahead of your cat besides the stock manifolds?

I've got my american thunder waiting to go in after i can get my headers on.

-chuck

 

Flowmasters almost always get nicer with time.

 

I love my American Thunder system! I did the single in/out for my turbo setup. Love the sound, though I wish it was louder. Turbo kills the sound, and I have nothing but 3 inch all the way back.
Enjoy the system!