can anyone tell me why it is my 96 gti wont quite reach top speed when gas selector is in regular run mode. when in reserve, the thing performs top notch but not the other. i guess its why the private owner presented it in reserve mode and told me a story why its the better thing to do when driving one. also, it runs at 51 mph with 2 people on it. should i be getting more speed over all? its a 717 cc. thanks