03 Altima 3.5SE misfiring at 4k rpm

[bobbo27]

i have an 03 Altima, 3.5 V6, under heavy acceleration the engine begins misfiring at 4k rpm...(only when the engine is warmed up)....when engine cold it will accelerate hard right to 6k rpm....(no misfire)I have NO CODES...!!! NO SMOKE from exhaust,replace plugs with Iridium IX's,properly gappedreplaced MAF with better AM600 versioncleaned throttle body

ideas??