I've searched and havent found a CLEAR answer yet, which glasspacks flow the best? Cherry bombs, purple hornies, thrush, ill even throw in bullets (even though not a true glasspack) I'm thinking of going with true dual 2.5" and glasspacks dumped before the rear. Cherry bombs are only 20 bucks and they are a classic muffler. But if something flows better and isn't that much more id go with them. Also what about using a 3" glasspack in a 2.5" system?

I'm not sure there is much of a straight answer to this one. Unlike a conventional muffler, a glass pack is basically a tube with fiberglass wrapped around it. The exhaust gas really isn't restricted or re-directed as with the mufflers that are standard on our car. I've always thought that glass packs were simply equivalent to straight piping from a flow standpoint. Dropping a 3" glasspack in a 2.5" exhaust would probably be the same as dropping a section of 3" pipe in there.

when i put a cherry bomb on my car it was where the cat was suspose to be and without it it sounded really loud and with it it was quieter but still obnoxiously loud

The problem with the typical Cherry Bomb and other glass packs is the perforated tube is smaller than the inlet, which leads to restriction. Using a 3" muffler in a 2.5" system would help alleviate that.

Bullets have the same size internal tube as inlet/outlet.

Dynomax Bullet, Borla XR1 Sportsman, Flowmaster Outlaw etc...

if you want a real glasspack, go with a thrush. i have one and no complaints. just be aware that true dual side exits are hard to do and it will cost you ground clearance. good luck!

Not necessarily. I think you are referring to a louvered core rather then a perforated core. Perforated core good, louvered core bad when it comes to glasspacks.
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Totally!!!!!!! I have gone through this before and it is a nightmare.

Save yourself the trouble if this is the case and spend good money on the proper pipes.

im not going to do side exits, im going to dump em right before the rear end. I think im going to go with thrush.

Get 2.5" thrush, they are straight through perforated core and the internal tube diameter is 2.5" all the way through.

Keep in mind that you'll need about 2.2 cfm per crank hp for optimum performance. 400 hp requires al least 880 cfm of flow. The pipe diameter is not necessarily and indication of it's flow potential.
I'm researching myself and came across a couple of web sites.

http://autospeed.com/cms/article.html?&A=0383&P=1

http://www.broaderperformance.com/mu...flow_tests.htm

http://www.ls1tech.com/forums/showthread.php?t=113572

You may find some useful information there.
2.2 cfm/hp means zero horsepower loss from backpressure. The tuning issue is something else.