My 1996 VW Golf GL 2.0 cuts out when I try to accelerate.?

I bought a 96 VW Golf GL, When I got it I put 85 octane in it, about 30 miles later it started cutting out really bad even stalling... My question is the guide says no octane less then 87. Is this a myth? I ended up puting a octane boster and filling the tank with 91.. IT is still running like crap.... Whats wrong? Can some one help me... The fuel pump and fuel filter are replaced as of this smorniong?