I've been running a 3.3 HPDI with all the Hydro Tec phase III mods for about 10 years. While it is not overly loud, the mods to the throttle body air intake make it noisier than a stock engine especially on acceleration. I have a fish/ski style setup and the intake noise is considerable for anyone sitting in the back seat.

I'm considering trying a vented engine hood cover like a Tuff Skinz. Has anyone noticed if a hood cover quiets the engine somewhat? Also, is Tuff Skinz is the only source for a vented cover for a HPDI?
Thanks