i had this same exact problem that your describing...is your a zetec like mine? it went away for a while when i changed the plug wires..actually went away for 3-4 months..its back now..i'm thinking maybe a bad coil, since it seems spark related.i changed the fuel filter twice in 6 months with no change in symtoms...my stuttering happens mostly it seems between the first acceleration upshift from a stop.if i really get on it, it does'nt seem to studder at all....let me know what you find out and hopefully what i did could help you..
