i assume that Proflow is similar to the Longlife system of straight through exhaust? If so I had a problem with booming sound level but cured as in this post:- made in this post "Stainless Steel Exhaust (cat back)" I had back box fitted by Longlife Thornbury Bristol last week,asking for the standard sound. I was told that the new exhaust would be a little louder than the original, but I was horrified with the result. The booming sound in the cabin in motorway driving was so bad that it hurt my ears!
I told Longlife I wasn't happy and took the car back today. They couldn't have been more concerned, fitted a different pattern tail pipe and hey presto problem gone and at no cost.
After they had sorted the sound level problem I asked them to replace the flexi which was on it's way. Again job done quickly and efficiently.
Great customer service and thank you Tim and Pete.)