CORRECTION: If you have a returnless style system, you won't be able to run a Dry System, but can tap into the fuel rail's schrader valve for a Wet System. I helped install a wet system made by Nitrous Express on a friends Cougar about 3 weeks ago.
If I had the money, I would go with a Direct Port System (wet system tapped directly for each port) complimented by a progressive controller.
The direct port system will ensure exact metering of nitrous/gas into each cylinder, whereas a wet system is just like a dry system that injects prior to the TB. Only bad thing about the dry system is that the cylinders nearest the TB get more nitrous than those farthest away from the TB. This can lead to a problem of running slightly rich in those cylinders ... rich you say? Yes, rich ... the extra fuel is being added, but the nitrous is not making it to the cylinder as planned. Not a bad thing, but definitely not running at peak potential.
Same holds true for the wet system except that proper mixing is occuring, just not as much is reaching the cylinders farthest from the TB.
However, the down side to a direct port system is that each intake runner must be tapped into, thus making the upper intake unusable without the nitrous system. However, you can always plug the tapped holes and still use the upper, but it won't look pretty. Also, the minimum that a direct port system can run into each cyliner is a 20 shot ... that equates to a 120 shot system. This is where the progressive controller comes into play. having 120hp at the flip of a switch will no doubt kill your tranny ... it could even bend a rod.
The progressive controller is there to progressively bring the sytem up to full power. So, when the nitrous is activated and WOT is achived, instead of 100% of the nitrous/gas coming online, only 50-60% is introduced, then the rest shortly later. This will reduce stress on the entire car by slowly bringing on the power. Down side to the system is the cost ... the progressive controller can some times cost as much as the nitrous system it is controlling. Also, a direct port system of this magnatude will also be dependent on the amount of fuel that can reach the fuel rail ... might need an aftermarket fuel pump to get the required amount of fuel.
