I was ordering a Dynomax Thrush Magnum Glasspack Mufflers resonator and they come in three sizes. Which size do I need for a 1994 civic coupe with a custom catback? 24.25 , 31 , or 35? Once I know i'm ordering.

 

BTW, its a 2.25" catback.

 

The bigger, the quieter. Get under your car and measure how much distance between the cat and the major bend near the gas tank. For the straight portion of piping can be replaced by a res.