I replaced the restrictive AutoZone muffler I had on my Mercedes with a Thrush Welded muffler. I'm very pleased! On the highway it isn't any louder than before, but around town the exhaust note is audible. At under $35 to my door I feel this is a great value.
The muffler I had before choked down to probably 1.25 inch pipe inside. High RPM power was really being hurt.