I bought my car (98 gts) and it had stock cats...quiet and sill/ footwell temps very high. Went to random tech high flow cars...less heat, IMO not much difference in sound ( previous owner had done a side exhaust conversion). Am now running no cats and a B&B exhaust...certainly loud and I do notice the smell but not overbearing. Very little sill heat now. I really prefer the sound without cats...I haven't had the level of fumes that fanboy mentions.