[cruiser_guy]

Ideally the turbo has runs of equal length from all cylinders which is why you see most all turbo manifolds coming off the center. It's also why most headers you see on high performance cars use header runs of equal lengths. The rationale is that each pulse will not interfere with the one before it since it has the same distance to travel. With runners of unequal lengths (like flipping a manifold) pulses can interfere with each other and cause a performance loss. What that performance loss might be I have NO idea since both of my trucks have a turbo manifold.

As for the turbo discharge, you want the larger pipe but speaking strictly from an air movement perspective the ideal pipe size is the turbo discharge diameter which would run for about 15 diameters and after which it could change size with a transition not to exceed 7.5 degrees. As you can imagine that simply does not work under the hood. You DO want to maintain the turbo output for a distance, I'd say into the downpipe, at which time a gentle transition could be made to whatever size exhaust you plan to use.

Also you would ideally run the wastegate separately but again, who wants an extra tailpipe? If your turbo has an integral wastegate and it appears it does, you want that wastegate to enter the exhaust smoothly and not have to make any abrupt turns. Personally that is one aspect that I really do not like about the turbo discharge that you have. I do not see any accomodation made for the wastegate discharge in your pictures. It looks like they simply put a plate across the turbo outlet and cut a pipe into it.

Of your setup, I'd change the wastegate setup first. The rest you can likely live with as long as the exhaust discharge from the turbo is not significantly smaller than the turbo discharge itself.