What's the best high flow cat to put on a 98 GS-T? I've seen universal and direct fit cats and theres a huge difference in price. I tend to shy away from the ebay specials because there are never any brand names mentioned...

2.5"? 3"? They are about $150 from any good DSM vendor.

I'm not sure what size to go for either. I have my 1G BOV and a boost gauge ready to install as well, and I was wondering what size/brand would be best..

Well if you are sticking with a stock turbo, or no larger than a Big 16G, go with the 2.5". It depends on what size exhaust you want to get too. 2.5 is good for those turbos. Larger, and you will want 3".

I'm sticking with the stock turbo for now, so 2.5" it is. I live about 30 seconds away from a Jeg's store so I guess I lucked out there. Shipping is a pain! Thanks a lot for your help.

No prob. Just make sure it is $150 or less from Jeg's. Otherwise get it from Buschur or someone similar :)