hiya guys i have a wrx import jst lookin to squeeze some more bhp out of it to be honest , jst bit of tech info required , i have de-cated the exhaust system curently but it literaly has one straight through pipe right back the back box now,am i loosing back preassure or is this ok as turbos dont need back pressure?, also i have a red top inlet manifold, can i do a straight swop or does the engine management need altering?

any help will be much apreciated , cheers fellas

 

For high power, minimal back pressure is required - when all you want to do is get those gases out as fast as possible.

For more modest power, then a 2.5" slightly restrictive system can help with adding a bit of back pressure, to help with scavenging - "pulling" - out the exhaust gases.

But if you have a free flowing set-up then it don't matter anyway - it's all good.

 

The red top manifold will make sod all difference. The only difference between a red one and a normal one is the colour. They are identical in every other way.

 

There are a few manifolds that could need mapping, e.g. a Spec-C on the newages delete the tumblers therefore causing a CEL and significantly improving the flow.

If your manifold is one piece and replaces the tumblers then yes remapping would be benificial - if it's still a two piece then no as it's just a coat of paint.

 

-Tubular Headers
-Up pipe
-Induction Kit
-Remap

 

I assume you have a Classic.
The only difference in the inlet manifold as Daz says is one has red paint and one does not. They are exactly the same otherwise.
On a turbo car you do NOT want back pressure whatseover.
Ported headers and matched uppipe after a full decat exhaust which apparently you already have.
After that you can up the boost by a number of means to achieve more power.