My recommendation is to replace the stock manifold and downpipes. Then go to a 2" cat, 2-1/4" pipe to the muffler, then 2-1/2 out the back.

The stock manifold does a great job and the rest of it just helps get the exhaust out of the way. It will also help keep your off-the-line feel the same as it was.

I had the LC Engineering setup on my truck at one point, but I lost some of the lower end. went back and did basically what I described. I like it much better now.

Just my thoughts.
Todd

1986 Pickup extracab longbed "Woody edition"
SAS - 33's, 5.29's, lockright rear.

02 IS300 SportCross - my "DD"
94 2wd v6 extracab
04 Outback Wagon- wife's/family car