I recently swapped out my transmissions on my b20 from a b16 to a gsr trans now for some reason, my car is dumping gas like a mug, ive gone from 30 mpg to 16mpg and my car smells constantly like gas, its not coming from inside its all coming from my exhaust, any ideas?

 

did you disconect the coolent temp sensor on the head if so double check that conector. also did you reconect the ground properly for the tranny.

 

did you unplug the o2 sensor on the header and forget to plug it back up when you bolted the header back up? (if you removed it)

 

Yes, this has nothing to do with the tranny, it has to do with the tranny installation.