goodmorning ,I have abit of a head scratcher,#3 cyl misfire.compression good 145 psi ,tail pipe readings 1700 hc 1.0% co . new tune up parts installed no different thuroghly inspected for possible vacuum leaks none found .Have a steady vacuum reading 19 in hg.inspected valve springs all ok,removed intake to inspect after installing no diff.what am I missing,any suggestions would help.Thanks in advance Rob K