1996 Tahoe Sputtering

We have a 96 Tahoe.  It Sputters when it is under light throttle & is worse when it is Humid or Wet outside.  My husband has put it on the scanner & the only thing it says is "Multi-Engine Misfire".  We Don't know what to do to make it stop.  He's done a tune up & changed the spark plugs, cleaned the screen, etc.  Can someone please give us some insight?!  Thank You!!

Did he change the Dist.cap & rotor?  Don't use the cheap ones.  Make sure to do the Fuel filter too.  Good luck!!

Also..could be the CSFI spider injection unit.
Has it ever been changed?
If not...and you can afford to do so, change it for the new Multec mini injector unit. This will deffinately eliminate any future injector issues you may have.