I'm happy with the homemade, invisible,Edelbrock muffler I was able to squeeze behind the bumper. Sounds great too. HOW TO: I bought a 2.25" Edelbrock RPM Series muffler at Advance Auto. What makes this muffler special is that it has 2 straight thru tubes in parallel which increases flow and allows for more sound absorption in a small package. Also it is made completely of 409 stainless steel. Look at the picture comparison vs OEM. Total weight of new system is 11#. HOW TO: Remove the stock muffler (easy, 2 flange bolts). The pipe leaves the stock mounting flange at about 135 degrees, which can be made from a 2.25" 90 and a 45. You can cut off your stock flange and weld it to the new pieces or do as I did and make a new one out of 1/4" flat steel plate and save the stock setup. Either way you will need a welder. Then slip the end of your new 135 degree ell into the muffler. Come out of the muffler with about a 4" piece of 2.5" straight pipe. I used 2.5" because it slips over the muffler exit and clamps in place. Then add a 90 ell and a tip of your choosing. I had a piece of 2.5" od SS tubing laying around, so thats what I used for my tip. Looks just like the stock one. Weld or clamp rods to the entrance and exit pipes to hang from the original rubber mounts. Adjust to center up perfectly. Total cost was less than $100. Sounds great, exactly like a Miata should sound, flows better, plus it weighs only 11 pounds. See pics to compare versus OEM monster. Sound is IMHO perfect.