Bad Injector(s) ?

[sierrahi]

Hi, thanks for reading.

I have a 2000 GMC with 5.3. I noticed the odd "shudder" when driving med. cruise, med. load condition. Since then I replaced the knock sensors (for a different reason), and therefore cleaned the throttle body, and replaced intake gaskets. I still have the "shudder", feels like a mis-fire, this condition also occurs at idle. I also will hear what sounds like fuel detonating in the exhaust, when I run hi -rpm's and the truck shifts gears (2-3 shift). No codes or Engine light. Can this be an injector(s) issue? I think I may have more than one problem. Also, I didn't disconnect the battery, and therefore didn't erase the Keep-Alive-Memory in the PCM. Should I try and put the computer back to "base" tuning?