hesitation and loss of power

[Squirt]

99 sr5 3.4 4x4 (cal emissions)
okay I'm a fairly decent mechanic and I can't figure this one out. been experiencing a lack of power and hesitation. Not a stumble/hesitation to the point of stalling, doesn't affect idle,has no problem starting.
Cleaned MAF (yes with MAF cleaner)
Replaced rear o2 sensor
plugs/coils/wires good
alt/battery only a few mos old & test perfectly
Replaced fuel pump/screen/filter earlier tonight totally expecting that to solve the problem ... got a tiny bit of power back but still have the hesitation...help??

 

[02-Sport]

My 02 I had had this issue under a load, at take off and when it would drop down a gear to pass. Plugs looked fine but changed them any way and it fixed my problem.
Hope you get it figured out, nothing more frustrating than replacing parts and still have problem!!

 

[Squirt]

yeah I was thinking of doing exactly that, only because I'm not sure when they were replaced last even though they look okay.