I just bought an 87 4+3 convertible. As with every preowned car I buy I try to renew it . The Vette got Mobil1, new distrbuter cap, wires, plugs , pcv ,filters ,mass air flow sensor ,tps , idle air control, EGR burn off and power relays ,Optima battery , GM fuel system treatment . I did not change the EGR valve. It seem as we drive the car , it starts to try to find an idle. It may take 2-5 seconds to find it from a stop 1500 rpm-700rpm. It does not have any codes or check engine light either flashing or steady. I'm stumped. Anyone have any ideas .