Wow that's quite a few disagreements! So we are talking about a 500 kw at the wheels build?
2. If you do need a bigger sump the Racefab sump (from Christchurch NZ) offers better clearance.
3. For a street car you don't want two Bosch 044s - they are so noisy. You may need two intank pumps - not sure the Walbro is good for 500kw. If you do need a surge tank you could find a location under the car.
4. Read the oil control thread on this site (or at least the last ten pages). You will need at least a catch can possibly with an air/oil separator but plumbed back into the turbo intake, not vented to atmosphere.
5. You want a 4in system right through, not narrowing to 90mm anywhere. I would run a central resonator with a muffler at the end but you might want two mufflers. With the right mufflers it should not be too loud.
6. Of course you should plumb your wastegate into the exhaust for a street car.