[Jack21]

If you're running a warm cam that lacks in idle and bottom end due to low vacuum, and it's a flat tappet hydraulic cam, you can get your vacuum up, and idle and bottom end improved by replacing your lifters with Rhoads variable duration lifters. They bleed down at low RPM and sound like you're running solid lifters.

Check them out at rhoadslifters.com. They've been around awhile, I've used them on big block Pontiacs, and they work great. If they made hydraulic rollers, I'd be using a set now