My 2008 Rx-8 currently has Re-amemiya header, amuse exhaust and HKS racing suction. I plan on getting a hi-flow cat. Are there any pros n cons? Which brand is best? What will it do? Will it make it any smoother or faster? Will it cause anything to the cel? Thx for you info..

is there something wrong with the cart you have now?

My car lags at 7000rpm in 2nd gear onwards. There is a gargling noise. I could kill those noises by slowly revving to redline each gear. Just in case if i haf to replace the cat, wat would the pros and cons be?

mmmm not necessarily the CAT..

I'm thinking coils .... and gargling could be MIAC

mmmm not necessarily the CAT..

I'm thinking coils .... and gargling could be MIAC
+1 I'd look into a GMC Yukon coil upgrade - like the BHR kit. I have one on my car and I'm very happy with it!

A highflow cat wouldn't be a bad upgrade to add later. To be sure you don't throw a CEL, I'd go a 200 or 300 CPI (cell per inch) all-metal cat. If you want the best flow (but possibly risk a CEL), I'd get a 100CPI cat.