What is the lest restrictive cat for a 98 civic ex? I have a boosted gsr and with a test pipe i start getting boost at about 3k, then i threw on a stock cat off of a buddies 96 lg teg and i didnt get any boost till almost6k! Obviously both are extreme cases, nothing or old POS plugged cat but what is going to be the most free flowing but still keep me legal?

 

cats even the best high flow ones are really restrictive for turbo cars. a lot of spool time and hp will be lost and you cant run race gas and high boost.
its best jus to run a test pipe and use the stock car when you need to smog