Just thought I should share my experience...
Got my manifold from one of the forum members, kabal, thanks mate. It was in decent condition, could see it came off a motor that had severely over heated, but apart from some cosmetic damage, it was fine.
Got the manifold cleaned up, got myself 6 new gasket seals from BMW, some bits and pieces for the vacuum rerouting and off I went.
Getting the manifold off was not too bad, the 7th nut was a real PITA and you have to be very careful not to drop it in the engine bay. The fuel rail also needed some sweet talking to come off. Once those were off the fun began...
After a few attempts I managed to fabricate the single hose that was the vacuum source for the idle valve and the other roundish thing, not sure what its called
used about 90cm of heater hose, some plastic elbows and a whole bunch of clamps
I also used a t-piece to join the other small vac hoses, and they all fitted to the M50 manifold nicely.
I also had to modify the IAT sensor and again, with some sweet talking and some ky jelly it went into the stock IAT location on the M50 manifold. I toyed with the idea of fitting it to the intake boot but I didn't like this idea, wanted it to look like it came from the factory...and I think I managed to achieve that.
getting the manifold back on was also a bit painfull, but nothing some flowery language cant help with
Once again, that 7th nut was a real PITA when re-fitting.
The throttle body puzzle was solved by using 2 OEM gaskets, one cut in half (very carefully), the 2 halves where placed into the M50 manifold and the TB itself, and the second whole gasket was sandwiched between these.
Refitted the fuel rail, this needed to be modified a little, one of the brackets have to be bent so that it can clear the mounting screw off the M50 manifold.
Fired her up, she sounded angry at first, but idle smoothed out and settled nicely.
Now the part I was waiting for, the test drive...
Initially I couldn't feel much of a difference. Felt like the engine management was having a conference and trying to decide where to idle and what to do during acceleration. She felt a tad jerky on the first couple of partial throttle pulls, but settled down very quickly. time for some WOT pulls

the torque loss is minimal, trust me. I found it really difficult to notice any lack of torque, but obviously there is a slight loss of torque lower down in the rev range (laws of physics demands it). But come 4500-5000rpm
wow! she pulls like a train. The stock 328i pulls hard till about 5000rpm and then falls away quickly, and now around 4500-5000rpm the motor comes alive. The difference feels massive, pulls very hard to red line. My car has ASC as well, so there is a beautiful whistle noise from the traction control throttle body, the extra air flow causes this, its stunning 
After a few days of hard driving she pulls even harder. The drive is factory smooth, idles like factory, everything is perfect.
I'm extremely happy with this mod, and enjoying this M52 even more now
Got my manifold from one of the forum members, kabal, thanks mate. It was in decent condition, could see it came off a motor that had severely over heated, but apart from some cosmetic damage, it was fine.
Got the manifold cleaned up, got myself 6 new gasket seals from BMW, some bits and pieces for the vacuum rerouting and off I went.
Getting the manifold off was not too bad, the 7th nut was a real PITA and you have to be very careful not to drop it in the engine bay. The fuel rail also needed some sweet talking to come off. Once those were off the fun began...
After a few attempts I managed to fabricate the single hose that was the vacuum source for the idle valve and the other roundish thing, not sure what its called
I also had to modify the IAT sensor and again, with some sweet talking and some ky jelly it went into the stock IAT location on the M50 manifold. I toyed with the idea of fitting it to the intake boot but I didn't like this idea, wanted it to look like it came from the factory...and I think I managed to achieve that.
getting the manifold back on was also a bit painfull, but nothing some flowery language cant help with
The throttle body puzzle was solved by using 2 OEM gaskets, one cut in half (very carefully), the 2 halves where placed into the M50 manifold and the TB itself, and the second whole gasket was sandwiched between these.
Refitted the fuel rail, this needed to be modified a little, one of the brackets have to be bent so that it can clear the mounting screw off the M50 manifold.
Fired her up, she sounded angry at first, but idle smoothed out and settled nicely.
Now the part I was waiting for, the test drive...
Initially I couldn't feel much of a difference. Felt like the engine management was having a conference and trying to decide where to idle and what to do during acceleration. She felt a tad jerky on the first couple of partial throttle pulls, but settled down very quickly. time for some WOT pulls
the torque loss is minimal, trust me. I found it really difficult to notice any lack of torque, but obviously there is a slight loss of torque lower down in the rev range (laws of physics demands it). But come 4500-5000rpm
After a few days of hard driving she pulls even harder. The drive is factory smooth, idles like factory, everything is perfect.
I'm extremely happy with this mod, and enjoying this M52 even more now