I would upgrade your injectors when you go to that 28R or RS. At a minimum you need to run the 370's at 4bar fuel pressure.
You'll need a wideband. You need to recirculate your BOV if you're running a draw thru setup. otherwise, a blow thru doesn't require recirculated BOV.
3" exhaust is a must.
Pressure testing the turbo system is a must, as well.