4000 midi inputs and outputs

If the MPC-4000 has 4 midi outputs than that means I can hookup 4 keyboards or should I connect the keyboard to the midi ins in order to record tracks on the MPC from the keyboards.

both.

4 midi outs means up to 64 keyboards/modules.

Or you can get real smart, hook up a MOTU midi xt, and get 8 outs and 8 ins. I Have all my mods hook up through a MOTU unit. Once you program the set up into the Midi unit, you dont need to power up the CPU or anything, works amazingly.