Drew:

there are a couple of good options for you.

The first is the JGS 4 into 1 manifold that puts the turbo in the same location as your origional manifold!! This will work alot better for you in the high boost areas, but remember, that might not be your only problem. Phase 2 motortrend made 526 with a log manifold identical to yours.

$750

Next up is the Enjuku 4-1 manifold made of 321 stainless and manufactured by Hot Shot. This is a great manifold for up to 420 RWHP.

$999
From 420RWHP --> you want the Full-Race manifold.
This is the same manifold Scott uses on his 540 rwhp ride

$1200