Has anyone used, or know someone that's used the Flowmaster Hushpower II mufflers? Do they like it? Any backpressure measurements?

I'm thinking of a setup such as this on an AMG 5.4L V8 engine:

a) headers
b) X-pipe or H-pipe close to the collectors
c) hi-perf cats (2 or 4 ?)
d) 2 Mufflers or one single 2-chamber muffler -- Magnaflow or Flowmaster (?) -- in place of where the resonators are. (hoping from there to the outlet is under 6', as I read over 6' might need a resonator)
e) dual pipes from there to the tail-pipe.
f) no muffler behind the left rear wheel.

- thinking would do dual 2.5" pipes all the way front to back. However one 3.5" pipe is also an option. I'd read a posting once that someone was recommended doing one 3" pipe by a DTM driver on the 1st-gen CLK55. But from muffler manufacturers, they say use a 3.5" pipe or 2x2.5" for my engine size and power.

(3" area = 7.06 sq.in.)
(3.5" area = 9.6 sq.in.)
(dual 2.5" area = 4.9 sq.in. X 2 = 9.8 sq.in)

- thinking headers. I read speedybenz's posting from a few years back on the importance of some back pressure the first 5 or so feet of the exhaust system, so I'm hoping using headers doesn't work against me. Thoughts?

- probably will do 4 2.5" cats like now to pass inspection, but hi perf cats. (?) Or can do two 3.5" cats (do they exist?). I don't know if it's necessary or if the 2nd set will be effective, as I don't how the stock 1st set is different then the 2nd set, and it can achieve efficiency (enough heat) in the 2nd set of hi-flow / hi-perf cats. Thoughts?

- Muffler: Magnaflow's got their Universal line, XL line ; Flowmaster's got their 30 thru 80 series linesand Hushpower II line.

I'm leaning towards the Hushpower II as it's a deep but soft/muted sound (you can hear the sounds on their website). I would be using two of them where the C43 has the resonators located. Hoping from there to the tailpipe is under 6', as they state over might need a resonator.
Thoughts on the Hushpower II mufflers vs. others?

Does anyone have any experience with the Hushpower II regarding performance / back-pressure? I'm looking for a lot easier flow then the stock C43 cats + resonator + single muffler, but don't want that at the expense of greatly increased exhaust sound.

In hindsight, I should have blew into an exhaust pipe (covering the other inlet) when my engine bay was empty during the swap to see "what flow now".

Thanx for your thoughts,
Steve

 

I have never hurd or used the hushpower, but have used the a number of the flow masters. The flow masters sound good at the low to mid RPM, but at the higher RPMs they make you exhaust sound like a jet and don't really sound good in my oppinion. I would recommend magnaflow, dynomax or borla if you are going to build the exhaust system your self. If you are going to use a hi-flow cat i would suggest using a dynatech hi-flow cat that you can buy from summit racing or jegs.
Hope this somewhat helps

 

That helps a great deal! Thank you very much for taking the time.