Does anyone know who makes the original equipment clutch? Are these any good or is there an aftermarket equivalent which is better?

 

Centerforce, Clutchmasters, and ACT all make clutches for the Maxima with higher-than-stock power holding ratings. I haven't heard much, but nothing bad about all three so far. From all the info I've read at this time, though, ACT sounds like a very reputable product.