but if it is Sun as in Sun Lu Chan,

then, there are xing yi and tai chi in Sun Ba gua.
Sun Tai Chi contain elements of Ba Gua and Xing Yi. To my knowledge, there is no Sun Ba Gua (that is to say, there was no individual style of Ba Gua that was developed and propounded by Sun).

You may be speaking of a different Sun (I know the name as Sun Lu Tang), but it seems too coincidental for that to be the case.