You have a return fuel system.
Don't worry about the reasons why NOT to run split fire or Bosch +4 plugs, just DON'T!! If you're going to be running nitrous, you'll need a copper plug(NGK TR-55). You should be fine with stock heat range with a 50 shot.
The 2.5L "should" handle the 50 shot like nothing, as long as your car has been maintained well.
You're on your own on finding a shop in Canada.
1: WTF is a Nissan Pulsar NX? If I'm thinking correctly, they are one of those little hatchback 4cylinders? My guess is that you should take him.
2: Please do a little more searching. You will find that a twin-turbo setup is NOT the way to go, nor is it really that feasable without a TON of money. There is no benefit to a twin turbo over a single.
Your car definitely won't run correctly with the 24# injectors, without a chip/tune. I would STRONGLY advise having the car tuned, or calling either ADC or Hypnotic Illussions Automotive for a chip/SCT X-Cal programmer.
Mark
