what would cause come and go hesitation?

i recently had the maf replaced and it seems that the hesitation gradualy worsens as the car gets wormer. ok to start i own a 94 3000gt sl. i have it to the garage twice doing things like shocks struts starter, and had everything checked out. it seem like when i drive it more then 20 min it starts hesitating(bucking) under medium throttle and it worsens over the course of the next 5 miles until and throttle causes hesitation and i have to shut her off. there is a very rich smell only when it acts up. the weird part is when she acts up and dies on me i limp her home and come back out the next morning and she fires right up and runs good. i have also had the lifter tick so i flushed the oil and started running fully synthetic( which she loved) but i still have the tick and when im in stop and go traffic she smokes so i think my vss are bad. the other symptoms are when she starts up with symptoms i notice that she idles at 600 and has no power when u rev it, backfires and makes a popping noise through the intake. replaced maf sensor with no luck please help!