Project / Build log: my ultimate daily

[NonoxX]

The project
Hi guys, I'm the happy owner of a 2010 N55 DCT 135i, with 250000km on the odometer.
I've been driving it for 6 years and 150000km, is full option, and really a super enjoyable car.
The car is FBO and pulls hard. Still i've never been really satisfied about that power delivery: getting 600 Nm till 4000 RPM is dope, but it tapers down real quick after that point. As a fan of high revving engines, that's a bit disapointing.
That's why I've been looking for a while to upgrade the turbos, to keep those 600 Nm as late as possible, but could never do it. Now I'm at the point where I can get some budget for the mods, have a workshop and a backup car during the work, so I can actually do that!
This project will probably start in 6 months to 1 year but I'd like to get really prepared and know what I'm heading at, and hope you guys can help me do the right choice.
The project is to achieve those performance goals while keeping an car that is nice to drive on a daily basis, without sacrifying too much reliability.

State of the art
Chassis
This car's chassis is already nicely modded:

• M3 front and rear control arms
• M3 font and rear swaybars
• Coilovers
• M3 rear subframe bushings

Engine

• MHD Stage 2+
• NGK 97506 plugs gapped to 0.022"
• Wagner Evo 2 competition IC
• VRSF catless downpipe
• Bucketless Walbro 450
• Aluminum charge pipe

The plan
Turbo
The center piece of all this project is the turbo. My choice is almost already done: I will go for a Pure Stage 2 or a TTE550. The final decision will depend on their price and availability (here in France), or even the opportunity to get a used one in good condition. I've seen that Pure released the Pure 750 which would give some headroom on the top end, plus has a specific manifold. Problem is being a bigger turbo it provides boost only on the high RPM, which is not ideal for a daily driven car. I would like to keep some low end torque, at least stock-like between 1500-2000 RPM, and I'm not so sure Pure 750 would do it.
Of course this turbo chage will come with a DV+ fitted and a wider inlet pipe.

Engine tuning
I'm most likely getting my engine tuned by a local tuner, for practical reasons. Not sure I'd take the risk to do it myself, although I'm willing to learn.
I will rely on the DME, I don't even know whether standalone ECUs are available for this platform, but I'm not planning an extreme dragstrip build either so it wouldn't make sense anyway.
I'd also prefer to stay away from the JB4: before going the MHD way I had one JB4 on the car, that worked well, but died after a few months only. This is probably just my experience, but I'm not willing to take the risk again.

Fuelling
I had a hard time to find reliable info about that. My N55 is an early model that means it has the N54 HPFP, which is known to have better capabilities than the later N55. Still, does it even have a chance to get me to the goals I set?
Most people reaching big power seem to move to PI, but I do not want that option because of the fear to run lean one day or the other, when a failure occurs and DME shuts down cylinders. There do not seem to be any controller out there that handles this properly.
Still, I couldn't seem to find much upgraded HPFP options for that platform... Have I missed something?

Engine internals
It seems not many people are upgrading engine internals unless they are pushing 600+ hp or so. Would it make sense to go forged for some parts to keep the car in the long run? It seems at least a preventive rod bearing change wouldn't be a bad idea, any experience about that?

Lubrication
It seems that oil starvation can be an issue on high powered N55. Are there some oil pan upgrades that would make sense in my case, or sump baffles maybe? Or is it just overkill for a road build that will never see slick tires...

Exhaust
My current exhaust is nice, gives a bit more sound than the stock one but not much. It could even be street legal from a sound level point of view, but France doesn't even give you a chance to get tested. A car must have zero mods. Period.
Still, as of today it is catless, but the gas smell in traffic jams is really inconvenient. An option would be to switch to high flow. I know I may lose a bit in perf, but it's a matter of compromise. Any model to recommend?

Gearbox
The DCT seems to be a pretty solid gearbox... I'll just make a full oil / filter / gasket service on it and flash XHP on it to get a bit more clutch pressure. No need for upgraded clutch packs or anything fancy when pulling 600 Nm.

The final word '(for today, maybe)
I know it's a lot of topics and questions and stuff... But I know I'll find here experienced guys and will definitely make this car an even much better car, thanks already to everybody that contributes!