I think the EQ6 pro might already have an autoguider port so it might not need the EQ mod. However while on this topic I have a basic EQ6 and have recently added an ST4 autoguider port as per the shoestring astronomy mod and it works fine. This might be an alternative to the EQ mod ?? it is very simple to implement and free if you want to buy the parts yourself and work out the wiring (although the kit is US$7) ...here's the link...
http://www.store.shoestringastronomy.com/eq_mod.pdf