I believe Flowmaster mufflers are bad for a turbocharged engine.
Gives problems with getting boost.
http://www.theturboforums.com/threads/339072-Why-Flowmaster-and-Turbo-dont-mix

Unless you are not concerned & don't mind leaving HP on the table, that choice is up to you.

I run a straight through design on my truck & is quiet when cruising around & idle, but when you step on it, it can be loud for some, but not as loud as a straight pipe exhaust w/no muffler.
Running no muffler = That means ticket time from the PO, PO, 5o, cops, if that is a concern? IMO, it is too loud & is raspy w/no muffler.
Not too loud but sounds like a loud pick-up truck. \:D
https://www.youtube.com/watch?v=cTS0smggZnE

https://www.youtube.com/watch?v=lQneJEltTxk

For the price, Devils own systems work OK.
I use Alky control system, rated to use 100% methanol.

Timing, you are not concerned about mileage?
Why not use the vacuum advance?

Every engine is a bit different, but best to dyno tune to see where max power is. 32-36 degrees range. *Note no boost*

You can run in the 40+ degrees while cruising, but you would need your vacuum can hooked up.

When you get engine knock, you can see on a dyno when the power drops off, you would then add more retard on your MSD box.

Again, hard to say where to set your max timing to initially.

But, depending on how much boost, what octane gas you intend to use, your manifold air temps, & other factors.

What boost level do you think you are going to?
What octane gas?

You are going to install your intercooler right away?

Start off @ low boost settings,2-4 PSI, work your way up.

I would say start off with 12 degrees total timing & work your way up, but,,,, need to answer my other Q's first, before I can think of more appropriate settings to start off with.

MBHD

12 port SDS EFI