From context I believe your are going with the PNP version, not making your own. If this is the case, I should be fully qualified to answer all.
The full manual is at www.mspnp.com
Yup, you'll want some injectors. Size depends on goals of course. No need for 550s unless you're going for over 300whp. Something in the upper 300s-lower 400s will do you fine for more modest ambitions. My last dyno run--the only time I've dyno'd with the MS on the car--showed low 70's% injector duty cycle with my RC 440 cc/min high z injectors. I hit 255whp on the dynapack. I'm already bumping into minimum injector on times with the 440s, so I would not want to have to go bigger unless I absolutely had to. The PNP will run lowZ injectors, so if I were shopping I'd be looking for something like the black top supra turbo injectors (low z, 440cc).
You'll get the IAT sensor from DIY when you get the MSPNP, so don't sweat it. FWIW, it's a GM open element. The only thing you need to concern yourself with is steel or aluminum sensor bung. Choice will depend on composition of your throttle body pipe.
MSPNP uses the factory coolant temp sensor located at the back of the head. Nothing extra necessary here.
There are 2 options for connecting the LC1 to the MS. Both are explained in the manual. You will not use the NB sensor with the MS and LC1.
Real TPS is the ****. Since you have neither A/C nor a superlight flywheel, it won't be as necessary in your car for idle valve control. But it will still help make your idle stabalize real nice when you come to a stop. It also does neat stuff for boost control and also datalogging. It is worth doing. Atl93LE has a thread you can search for where he lists a BMW TPS (with part no) that is as easy to install as it gets.
Jerry has provisioned the MSPNP to be compatible with CA sequential injection cars. Shouldn't be a problem, but it won't be a bad idea to touch bases with him on the issue.
EBC is the ****. You'll need a 3 port solenoid such as the GM Typhoon/Cyclone sensor. Get it from DIY if they have any in stock, if not they are at the Chevy dealer or GM Parts Direct. It will require running 2 wires, one is +12V the other is ground and goes to the center plug of the MSPNP. I sourced +12V from the diag connector; simply opened the connector, spliced the +12V pin (I think it's called B+), and closed the connector again. The wiring looks stock. The ground wire gets run to the cabin to the PNP, which will control the solenoid by adding/removing ground.
Open loop boost control works great, no complaints. I've played some with closed loop control and it seems like it works well too. But I'm yet to give it a gold star just because I haven't played with it enough yet. But boost by throttle position and boost targets do seem to work correctly. Closed loop control adds 2 safety nets: Boost cut with high intake temp and boost cut with knock. Closed loop is not possible w/o the TPS.
I had some ground issues. I would recommend beefing up the ECU grounds proactively. Just run 3-4 16ga wires from the pass footwell through the grommet by the washer bottle to the back of the head by the fuel rail. There are 2 sensor grounds there, you'll see them both. Remove the hardware, clean the area the grounds contact with a dremel or similar, and attach the wires you ran with some ring terminals. Use one of those wires for your LC1 and gauges. The others are for extra ECU grounds. These extra grounds are good to have, especially if you're going to have things like boost control and low z injectors.
Get yourself a knocksenseMS. It will run you just under $100 shipped, but adds real active knock sensing and logging to the MS. The MS can lessen advance and cut boost with knock. Good stuff. I didn't order it, but mine came with the LED as well, which will flash with knock events.
Also search for Atl93's thread about the Palm software for MS. I haven't located my Palm, but I saw his. Very nice package. It's something I keep meaning to get around to.
Long thread. Payback. I'm going to go drink a beer now.