SB Dual Plane Intake Manifold

Really you should post what car you own and what your motor has as far as H.P. ,camshaft and bore. Rear end gear, trans and if auto what stall. The LD 340 is good out of the hole up to 4500 RPM usually with a hydraulic camshaft. It is old school technology from the early 70's. The parts today are way advanced and there are better combo's out there. The performer RPM dual is a good one but again comes down to what you have. The LD 340 is just a tad better than stock for back in the day. Given more specifics would help you greatly.