acceleration irregular

99 silverado has hesitation during steady, medium throttle acceleration.
replaced fuel filter, spark plugs, used fuel injector cleaner. could the problem be electronic in nature?

1. Is the engine making any pinping sound?
2. Get a code reader. When you have trouble code you get a service engine light but if you are getting pending codes they will not show up.

3. Have you washed the engine bay lately? - everytime I do this I get problems for a couple of days.

Things to do?
1. Check spark plugs wires for lose or broken ( Check resisteance )
2. Coil check primary and secondary or just replace.
3. Take a look at the cap and rotor are they wore out?
4. You might have to have you fuel injectors cleaned. I do it my self every 6 months. $150 for the adapter and $10.00 for a can of pro clean. Its hooks up to the fuel rails. Make sure your fuel pump is off
5. Clean the trottle body for build up.
6. Bad Fuel?
7. Air filter? - clogged

Also check fuel pressure regulator.