Is it safe to run the car without a cat? I was thinking of putting on the ultimate racing long downpipe and the resonated test pipe? If this is a good/bad set up, please let me know

 

Its a good setup power wise as long as you get it tuned... the afr may get a bit wacky. You may throw a cel w the o2 sensors but just disable them. As for emission laws in canada, i have no clue. Its illegal in my state to run a test pipe.

 

How much HP can I expect from this mod?

 

Whether you ditch the cat or run a high flow one, there is definitely power to be made.

Bryan did a bunch of testing:

https://www.evolutionm.net/forums/09...ly-work-2.html

On a completely stock exhaust system (on an Evo X that was tuned), a test pipe netted 15whp and 17wtq according to Bryan's dyno tests!