Engine only backfires up thru intake when over 50 mph. Otherwise runs decent. Comp chec all cylinders (4) and are 180 psi +. Disconnected EGR (plugged) and problem persisted. What am I missing? Valves/springs...??

Check ignition timing, check timing belt to see if it jumped a tooth, check the condition of the plugs

actually i think it's a timing CHAIN....

Try some Seafoam. Stuff works wonders.
http://www.seafoamsales.com/motorTuneUpTechGas.htm
-Cory