Intake Manifold will actually raise your 60' times because your engine will be bogging, due to less air velocity into the cylinders. Unless you have a turbo or more aggressive cams, don't invest in an intake manifold or throttle-body. Just work on your launch. Tweak the tire pressure so you can get better traction out of the holeshot.

A header would be my next move along with a hi-flow cat.