When did Stillen start shipping these?. I remember there used to be the "equal length" ones before.

 

Stillen started shipping the universal Y-Pipe soon after the 1999 model-year CA-spec Maximas came out. the 1999 CA-Spec Maxima uses the same Y-Pipe design as the 2K, which is different from the pre-1999 models. Stillen's solution is actually pretty ingenious, having the universal-fit 2-piece design.

There has been debate about the "equal-length" design. I guess Stillen discovered it wasn't worth the extra expense.