brief loss of power or hesitation on 03 3.4 with 195K

I just purchased this truck, I had a new timing belt, water pump and thermostat changed seems to run fine. Just piece of mind to know when that service has been done now. I had a check engine light, the code pointed to the O2 sensor, I have changed both - the one in front of the the CAT and the one behind the CAT. I also changed out the fuel filter. Now I get a slight drop in power about 2 seconds in duration. I also experienced a hesitation coming off of stop so from 1st gear going into second the Taco lost power and then went back to normal.

Any thoughts on what this hesitation or loss of power could be?

 

check or clean your mass air flow sensor