I just recently installed a revo short shifter for my car and it feels nice in aspect of having shorter throw, but i've been hearing rattling everytime i go into 2nd and 4th and 5th gear feels stiff, and not only that in neutral all the way left feels stiff. So I'm wondering if anyone has had or heard of any problem like that.

 

check your clutch line in the engine bay, mine used to rattle, turned out the clutch line was rubbing against my transmission, i bent it out of place and it's ok.

about it being stiff, try putting grease on the joints of the shifter itself, if that doesn't work, go to your normal shifter and see if the problem is still there, if so, it's something in your transmission .