2001 Ford Expedition V8 Two Wheel Drive Automatic 77,000 miles

repl.egr, epde sensor, vac sw to egr,cleaned egr tube restictor office and sensor(epde)feed tubes,repl aig valve.If I apply vac at idle to egr eng rpm drops low.no vac leaks that I can detect.new plugs& spark towers. eng runs good. error seems to happen with hot eng. low to moderate ecceleration from stop. at idle I get the following results,ect(f) 189,dpfe(v=.15),egrvr=0,ftp(v)=1.59,iac%=31,iat%=93(f),iat=2.35v,1mtv(%0=0,tp(v)=.99,maf=5.17,maf(v)=.84 ,fpde imput voltage=5v. During winter months only I get insufficant air flow to bank 1 . about 2 times in one winter, then one for bank 2