I achieved some modest gains with better exhaust on my 55.1 235.
It's stock except for a Corvette exhaust manifold and dual exhaust with 22 inch Smithy's.
dyno results I picked up 11 lb-ft of torque at 2000 RPM, about a 6% gain,
and 6 HP at 3000 RPM, about a 7% gain.
Measured at the wheels.
Cost was about $700 IIRC, since I built the front exhaust pipes myself.
It's nothing like the Cummins turbo diesel brute in my 04 Dodge, but I consider the 235 pepppy enough to be fun to drive.
regards,
Leon
