Any under the valve cover work I should do

Hello all. I've got a leaky valve cover on the rear passengers side of my 2006 4.0 tacoma. Is there anything else I should do while I've got the top end exposed. Another thing I was curious about. I don't have the extra cash for headers at the moment but I was contemplating hollowing out the front catalytic converters. Has anyone done this or know of possible problems I should be aware of. So far I've added a URD Y-pipe and an AFE CAI. Any suggestions would be greatly appreciated.

 

if that is the case with altering the converters then whats the deal with headers. dont they reduce the back pressure even more

 

valve clearance check intake is 0.006-0.0010 in.(0.15-0.25 mm) exhaust 0.011-0.015 (0.29-0.39 mm) on the 1gr-fe engine