Cabrio has no power and stutters no diagnostic codes. Tach and speed work interm

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when cold starting car acts normal. It will drive normal till it starts to warm up and then loses power and stutters to where I have to down shift (manual trans) and not try to go over 60 mph! After temp get to 220f it seem to settle down a bit but is still sluggish. Replaced plugs, wires, cap, rotor, distributor. replaced vacuum hose(1/4 in) from air box to intake. Flushed radiator and added new coolant. Checked cat for flow, that was good. try to hook up diagnostic and no codes but the tach and speedo only work when it is cold. Once it warms up and I try to start it, the speedo is dead and the tach jiggles at 0 and will not respond.