I reached out to several of the Cobra Kit mfgs. a while after I started building the Cobrapacks & NONE of them had any interest in offering a better flowing muffler with their kits (except for Lonestar). Factory Five asked me to quote them & my mufflers were about $25.00 more apiece than the ones they were using already - they said "no thanks - we'll go with the cheaper ones." All they care about is the $$. I suggested the car owners just MIGHT spring for a little extra $$ to gain some major HP - they disagreed. They must know something more about this than me - I dunno. One of them said they had never heard about the Cobrapacks - they didn't want to know any more than that. Great attitudes - I was really impressed.
