I had a set of Cobra's on MGM, butt dyno felt like it lost poop.
Switched them out for TBR's. This set had a before and after dyno run.
Before was with Cobra's, HP 93 forgot torque but it was very low.
Went to a set of MarkT's glass paks, early ones, with the screw on adapter.
Dynoed at 96/86.
Changed them out for a set of Viking with an added crossover, and some added head work, ported & relieved.
Dynoed at 106/96.9.
Here is the crossover I built for the system..

This is the NASCAR pipes I built on the Chevy Trike. Sanderson headers and from there to the rear was my work.

I used a 4" NASCAR muffler and welded the ends on it to adapt to the header and get the turnout. The turnout is also labeled NASCAR.