I used 2 inch tall open spacers because it is a big motor and we were running WOT on the dyno. I didn't try it without the spacers so I'm not sure how much it mattered.

The Performer RPM combo used a 1000HP Holley carb. That combo made roughly 20 more ft-lbs and 20 more HP than the CH-28. So only a 3% difference on this motor.

The CH-28 setup with the dual 500 cfm carbs ran a lot smoother than the 1000HP Holley. The motor sounded like a stocker with the CH-28 installed.