[Euro Ford Fan]

To answer your question nobody who wants big HP numbers.

But it's more about what you can put up with day to day rather than what you will accept for a trip to the strip.

Look at puppets car it makes decent power and is no louder than stock. Frankly I would consider accepting the restrictions and backpressure plus the loss of maybe 10HP to have a car that I could live with every day.

My simple theory on this is that if your running any sort of forced induction you want to get as much air into the motor and consequently as much air out of the motor as you possibly can. For big HP backpressure is your enemy.

Since I never successfully turbo'd my Focus I can only use my XR's for comparison.

My old 88XR made 199HP 205TQ after its motor rebuild everything was totally standard boost was at 15psi. I went to a full 3" system downpipe - tip and picked up 26HP. Most of this was HP I believe was gained with the addition of the 3" downpipe and the swap to a 3" cat. I don't believe the 3" pipe made all that much difference because I simply wasn't running that much CFM through he exhaust.

Now on my race XR I swapped the head from a stock unit to a PM Motorsports Stage 2 with a 480 cam and it went from 246HP to 298HP I then swapped out a gutted upper intake and ported and polished lower for the PM Motorsports Log Manifold and picked up a further 32HP. I know I could have see even more HP with that gain but at this point my turbo simply could not produce enough CFM to fill the intercooler, pipes and the new intake manifold this was plainly evident on the dyno chart.

As for the exhaust side a swap to a SS tube header shows gains of on average 40+ HP over the stock ported E6 manifold. That was on a mildly modified car running about 20PSI on the stock turbo so my suggestion if you can only pick up 3 or 4 HP with the addition of a race header on a blown application don't bother because there is a bigger restriction that needs dealing with somewhere else in the system.