Manifolds lose power everywhere compared to long tube headers but the difference isn't as much with a small cam. I have Hedman tight tubes on my Duster which fit great themselves but the outlet location sucks for routing the head pipes, bought a set of Doug's D-453 about a year ago to replace them but haven't gotten around to it. To make the exhaust not go under the steering linkage I had to use angled collectors and fab head pipes from 2 1/4" mandrel-bent "donuts". It works but I'll probably pick up 30 hp and torque everywhere with the Doug's.