Opinions are like arseholes so expect many replies
I have made so many exhaust manifolds I care not to think back too much about it, I now only use on FD's the HKS T04Z manifold. This unit is "perfect" for a two rotor, the runners are ideal, the position is as well. They are very durable and you wont get anything better made by anyone.
The most important bit is the power and the response, I use a turbocharger that will deliver over 750bhp @ the engine (I run it now at around ~580 to 600bhp @ 26.5psi), it clears everything with ease and this is with a "large" turbine. The before mentioned response is something I have never seen on ANY 13B street car or race car @ this high power level, I can stand on it form only 5000rpm turbine speed (not engine speed lol) (around 2500rpm) in 2nd gear and it literally launches down the road like a cannon ball being fired! it is "unbelievable"
Don't place too much credit on BS dyno graphs showing you "spool to rpm" these things artificially load up the turbocharger and give it too much time to build up shaft speed and thus boost, what you are interested in is transient response all the stuff that happens from a closed throttle to your red line in under around the ~ 2 second range. A real mega set up car will accelerate so quickly in the gears (using stock Mazda gearbox with tires and final drive to do 210mph!) that you will almost find it pointless once you own one and drive it. This is what a quality manifold and turbo set up will deliver you, rather than the token 600rwhp dyno sheets some sprout out on the interwbz.
A Garrett T04Z with appropriate rear housing and HKS exhaust manifold with a Tial V44 wategate and a minimum 1.3 bar spring in it and you are on the way to a sweet combination, all you need then is a decent motor, a good engine calibration, and a decent electronic boost control too.
Here is a pic of how my turbo sits, I run a T04Z based turbo (modified by me) and a HKS manifold, 3.5" exhaust made by me and all heat shielded and using the factory carbon air box.
Some performance figures
O.K. Remember pump petrol/gasoline here only !
***OFFICIAL VBOX test results***
90kmh-140kmh = 2.26 seconds!
100kmh-150kmh = 2.39 seoconds!
100kmh-200kmh = 6.25 seconds!
Still on old tires, and showing about 24psi boost on the VBOX, and ~330rwkw VBOX POWER
Tested at 1320kg run weight and 25 deg C ambient day, still doing boost learning procedure so there is a bit more in at this level and fuel mixture set rich to be on safe side.
Fact V's Fiction
Will put up some VBOX graphs when I get them off the lap dancer top
Here is the graph of the 2.26 second 90-140 test 
this car has a *massive* power band, not normally seen on genuine 13B road cars of this level of performance and speed!@ the word "response" does not do it justice! It builds one bar of boost at around 3400rpm in a transient test, and near its maximum boost setting well before 4600rpm and it does it even in the low gears which only take a second or two for 8000rpm, its fantastic..... best road car set up ever !@
