Welcome to the forum to start. Now I will try to help you here okay. All verts offered in the US were non turbo, which is a 6 port 13B. The power was different between the S4 (86-8
146hp & the S5 (89-91) 160hp.
No timing chain or belt on the rotary, no cams, no valves. Port timing handles the needs of these parts on our motors. Check our FAQ section under porting.
I was never a fan of the vert seats, I personally would get a set of non verts or aftermarket seats over reupholstering those.