Problem exhaust drone: Solution 1/4 wave, or Helmholtz resonator?

[Dave W]

Dan
See if you can get a copy of "Scientific Design of Exhaust and Intake Systems by Philip Smith & John Morrison" from your local library.
The location of the "J" pipe in the system and distance from the muffler will effect the resonance frequency as much as the length, i.e. volume, of the "J" pipe. They appear to be most effective when install right after the exhaust manifold. Dave W