Losing throttle response intermittently

[alkaline]

Put a new battery in the truck not because it was bad, but it was 5 years old and from the previous owner. Wanted to get a fresh one in. Battery holds charge, gives ~12.5v on the meter when off and ~14.5 when on. This issue started immediately after changing the battery but I don't think it's related but wanted to mention anyway.

The issue:

When driving at low speed, usually in 1st or 2nd (manual), the truck will surge or hesitate (feels like driving with someone who is learning how to drive a manual) and the gas pedal will do absolutely nothing for a short period, it's very apparent at low speed. When I am in 4-5 gear it does not surge or hesitate in the same way but again the gas pedal does nothing.

This can happen all the time (its nearly undrivable) , or infrequently (once in a 10 minute drive), can happen immediately at the start of driving or start happening a few minutes later.

I thought I'd get lucky when I changed the fuel filter since I hadn't since I bought the truck in May. No change. Gave it sea foam for the first time through the fuel and intake and again no change.

I opened the ECU and did a visual check for leaky caps. They *look* 100% fine to me but I am going to change them ASAP anyhow since cap failure is not always visual.

Whaddya think?