y pipe
 

whats the difference between a ls1 ypipe and lt1 y pipe? I'm talking about for long tubes.

I think it might come down to the angle that the y-pipes connect to the headers. If i remember correctly LS1 headers (when looking at them underneath) branch out away from the transmission as LT1 headers are a little more straight on. Also each companies y-pipe varies as they are typically designed to match headers.

Bingo^