I have a 1999 4x4 4runner, automatic with 82,000 miles.

sometimes when I tromp on the gas to get around someone, it hesitates for a second and then it takes off.

this normally happens at slower speeds, like 10-15 mph to WOT. it just started doing this.

I have it in the performance shift mode all time due to the hills here, I hate when it shifts to 3rd while going up a hill in normal mode.

I do have the deck plate mod and a K&N filter, but those have been in for 8 months now, and it has just recently started doing this (maybe 2 weeks now).
and its not every time.

any clue??