Upgrade your out-dated intake manifolds with these higher flowing ones. In 2000 the 3100 was outfitted with these bigger style intake manifolds from the factory. Only the 3400 had the 56mm throttle body. The 3100's had a 52mm unit. This upgrade will yield about a 15hp gain.

Kit includes:

• 3400 style upper intake of your choice
• 3400 lower intake manifold
• All the AC Delco gaskets and hardware needed for the install.
• slip-fit heater tube if needed (depending on vehicle)

3400 heads have 1.76" intake valves and 1.425" exhaust valves.  Early 3100 heads have 1.72" intake valves and 1.425" exhaust valves.  Therefor the 3400 intake valves are .040" bigger, and the exhaust valves are the same size.  The extra difference just means the 3400 heads breathe a little better, and have more potential to make more power.  We do not have dyno results for this difference.  It's probably not a huge difference, but it's one of those things where every little bit helps.