Originally Posted by engineerx
Another well-known tuner here in the the US reported this on a Perrin & stock header thread:
Notice how he says the EL headers "lost" power @ higher rpm's
I've also heard the same comment from another very well-known and experienced tuner. The Perrin EL headers work great in turbos smaller than yours. The engine is an air pump. restrict the outlet and you can't take in more air than you can pump out. The turbine is pumping air into the engine once fully spooled (higher rpm's) but the engine can't use all of it because it can't pump it out. In this case, you will still see your boost reach very high PSI's but it doesn't mean the air is making it into the cylinders.
That's my best guess. Alot of good suggestions from others here. Now, there could be other reasons. So you'll have to carefully analyze where the system is choking.
Good thread.. we're all learning !
Thats a fair comment, and I will look into it further i.e full race manifolds or UR.. but if i change the manifold if the restriction is in there then it will move to the upipe as i cant change the diameter of the upipe twin 38mm IDA pipe as it will hit the steering coloumn.
So changing the header will it still be beneficial??