Stumbling during acceleration

1999 Tacoma 2.7l 5 speed 4x4 205,000 miles. Truck idles at around 700 rpm's and is smooth. Runs good driving around and shifting at low rpm's but if you take her above 3500 it seems to have a hesitation. It's not always but it is happening more often lately. I have replaced both coil packs, wires, plugs and fuel filter. I plan on pulling the throttle body and cleaning it good along with the IAC and TPS. Just wondering if anyone has had any symptoms like this and what fixed it. I hate to just throw money and parts at it but it is getting annoying. Could O2 sensors or fuel pump heading south be the cause? Thanks for any suggestions y'all have...it is appreciated.

 

If you have not checked the mass air flow sensor, give that a look. I had the same issue. Take out the 2 screws and lift the sensor from its housing. Mine didn't look dirty at first, but under good light the underside of the 2 wires and resistors were coated in soot. I used rubbing alcohol and a cotton swab to very gently clean them. Fixed mine, very quick and easy.

 

My hesitation was the front o2 sensor, bought a Bosch one and it still hesitated. Through in a factory Denso from rockauto and problem solved.

 

Cleaned the maf sensor, throttle body and all. Replaced both O2 sensors with new bosch ones. Now the hesitation is really bad when you first start it up but gets better when it warms up. Hate to change O2 sensors again but maybe I need the denso one for the front. Thanks for the replies.

 

Lift your truck and check how much the wheel spins. Your brakes might be draging . Also feel the rpms with your foot . And see if its the motor is stuttering .