wierd miss, any ideas?

[adictd2b00st]

ok over the past 2 weeks my car has developed a miss under boost around 4500-5500 rpms..... its most prominent in 3rd gear but once in a while will do it in whatever gear i downshift into. the wierd thing is tho, once it happens, i won't do it again while i'm going thru the gears. like say i downshift into 2nd.....it'll do it in 2nd but not 3rd and 4th....... if i downshift into 3rd it'll do it but not in 4th etc. i pulled the plugs today, they seem to be burning fine, look to be running a lil rich but nothing too crazy. any ideas? only happens under WOT, partial throttle its fine

prominent mods: t28 @14psi, 300zx maf, afc (needs to be tuned, but it never used to do it before so i don't think its a tuning issue?), walbro pump.......... with stock injectors/fpr