Mine was doing this a lot when i had the stock plugs. I changed to 0.8mm I had to anyway running higher boost and the pop went away. It occurs seldom now. As for power depending on what ECU you get.
ECU (try getting a stand alone with more control Adaptronic,Link,Vipec, Haltech etc piggy back do not have as much control as you do with these.
AFM (you might be restricted up to 250kw, AFM goes out of resolution you can still tune it beyond though. (MAP and IAT sensor) if you dont want AFM. Turbo (Cant go past Hypergear do some research for what suits you, smallest sized turbo that can produce what yo want) check out RB25 TURBO UPGRADE DYNO RESULTS in Forced Indution
Fuel pump (Nismo,Tomei pretty much plug took me 20mins. Walbro 500hp etc)
Injectors ( you will also need to consider if you will use E85, if so project how much power you need and use this calculator (http://www.injectordynamics.com/HPCalculator.html) (IDxxx, Xspurts, Deautshwerks) or ASNU (what im using )
Clutch (Your wallet will do the talking) NPC is very cheap and does good shit otherwise exedy or some other spec.
Coilpacks (Yellow Jacket, Splitfires)
Depending on your temps you might need a new radiator the GTT radiators are very small. Change to a forward facing plenum(you can relocate traction control)
Also you should do some geometry work. Might be able to put down the power better and enjoy the car.
Changing headgasket might be ideal but a lot have done it without but i would if i had the coin. Making power inst hard but making reliable power is where the issue is.