Today I actually had the opportunity to drive my car on the freeway. With the 6-speed manual, I'm able to get the RPM's down to about 2000 while driving at 70 mph. I have one big problem with that... The drone is absolutely unbearable at high speeds. I ended up dropping my speed to 60 mph where I was cruising at 1500 RPM and the car was as quiet as a church mouse. My only other option was to speed up to 85 mph where the car was cruising at 2500+ RPM. While inspecting my engine bay during my lunch break, I also noticed a bigger problem, that my headers are resting directly on my steering box.

So, I need two fixes: 1) Is it possible to move/shim the steering box or engine so they won't contact anymore? (I have a cherry picker) 2) What's the best way to get rid of the drone?

My 408 makes about 523 hp. I have TTi shorty headers, TTI 2.5" X-pipe, Dynomax Super Turbo mufflers, and turn downs. I realize that the 2.5" diameter is undersized for the amount of peak horsepower I'm making, but I needed the 2.5" exhaust to ensure everything cleared the undercarriage.

Changing the muffler will probably be the easiest way to get rid of the drone, I just don't know what style of muffler to try to remedy it.