Does anyone know who makes cast iron manifolds for the stock turbo? I want something that will spool up faster and give me more top end.

 

aps makes a cast long runner type for the stock turbo. btw you get faster spool at the cost of torque with short runner. if you wanna be raw then just get your stocker extrude honed and ported with a nice coat (would cost you less than a new mani) and that'll be good for quite a lotta spool and hp.

 

you have any idea how HP increase you can get with porting it?

btw do you have to port the 02 housing also?

 

iunno... no one has done it yet... buschur is working on porting it now in anticipation for the 20g. i think it will be promising and if anything the increase in flow capacity will most critical... it won't be a bottleneck for anything. as for your 02 housing... i suggest getting rid of it in favor of an o2 eliminating dp... less parts less fuss more direct more power. just get a well made one... one that has few welds and whatnot and is smooth on the inside.