[quote=RIP;6520908]How long between the tune up and lack of power? What did the tune up consist of?
Weak fuel pump? Connect a pressure gauge at the fuel rail. Should see a steady 55 psi. Lack of power at speed is one indication. Sag or stumble on acceleration is another.
Timing off? It has to be checked with a capable scanner. If you want to throw parts at it an upstream O2 sensor would be high on my list.
Changed plugs , wires, thermostat and 02 sensor the one on the exhaust before cat