I have the Stage 2 D1SC and its been great. I do have alot of opinions about the install, parts required, ect since it is fairly recent on my install. It will definately wake the car up, and is a hell of a lot more fun. Be patient with all aspects of the install and tuning. Do not expect everything to fit exactly right, or for the first tune to be perfect for you.
Proper injectors (which are usually not in the Procharger Kit), the new ATI crank balancer which you will need (again not shipped with the kit) spark plugs, Boost a pump or new fuel pumps are not included in the Stage 2 kit. The vendor you bought it from probably is looking after those parts for you, but do not overlook these pieces.
Make sure you check the items shipped from Procharger to ensure they shipped the correct belts ect.
1) get the wide band 02 sensor and A/F/R guage to be safe and for tuning purposes. A boost guage is nice to have also.
2) Spark plugs. I only went 1 step colder, but I may change to go 2 steps. My car has been running great on 94 octane, but on 91 I get some STKN on the sensors. ( we don't have 93 octane in Western Canada and only Husky/Mohawk do 94)
3) Look at getting wider tires on the rear end. You will want a larger footprint to go with the power.
4) If you are having it installed by a third party, learn as much as you can about the install so you can change the belt later, change the oil in the head unit ect. If your doing it yourself, be patient and know that its not an 8 hour job. You will be relocating pieces, a little trim work, and certain components are tightly fit. When its done though it looks great.
5) have the belts tightened again after putting some miles on the car. Also have the alignment of the belts/pulleys again.
6) I changed the oil in the headunit for the first time when we tightened the belts. (roughly 600-700 miles) Now I will do it according to their specs of 6000 miles. The helical gears are nice and the noise is acceptable. It provides a nice whine but at first it can seem loud and unusual. I found it got better after putting miles on the car.
6) Use the initial tune to get onto a dyno to ensure you are running safe. It will also provide you with more data to get retuned., Have it re-tuned as you get some miles on it. If you can datalog and send them to one of the highly regarded tuners around do so.
I did most of my research on this forum and from talking to people on here. There are some great people and resources available. Hope you will be happy with your Sc'er.
Ryan