Shearer Fabrications manufacturers tubular SS headers with this feature. With a 5 bolt housing that does not also function as a wastegate flange, the issues of housing are diminished in concern.

Most of the vendors I've spoken with simply don't offer a 4 bolt housing due to A/C interference. The SS tubular manifold mounted wastegate and a V-band exhaust is the way to go.

 

we've tested the 4bolt T31 housing vs. the ford 5bolt housing in a ~400whp nissan application.

same turbo(GT2871R), same boost, no changes...

baselining with the 5bolt housing and the T31 4bolt gained 20whp.

and just to toss it in there, we only use the T31 4bolt housing in all of our turbosystems. including our HVS topmount kit with a 3" 4bolt to vband adapter for the downpipe connection.

hope this helps

 

Cool, so the 4 bolt gained 5% more power.

Any change in spool characterisitics?

Any other differences besides an increase in power?

 

We use the 4-bolt 3" TH on our 30R and 35R kit too. We have had excellent results all while retaining the AC.

Good luck!