I am adding about 100 shot of dry nitrous to my car. I got the TR-6's cause everyone says you should run them if your running nitrous. My friend who knows a crap load more than me with cars said that the tr-6s arent necessary and that I could run the chance of fouling my plugs. Should I leave the tr-5's in or should i go a step colder and run the 6's?

 

Certainly the TR55's are more ideal for the stock motor but the rule is one step colder for every 50 or 100 HP (can't remember which) increase. I have never heard of anyone fouling with them.

 

TR6's good up to 150. IMO they are a good safety for the price.
As far as fouling, you shouldn't run N2O if you can't tune your car.