gmc w4500 dts Code Problems

Hi I Need Some Major Help We Have A 2001 GMC W4500 With The GM 350 In It We Have Been Having Engine Codes Coming Up At Randon And When They Do It Runs Like Shit We Can Erase The Codes And Will Sometimes Go Two Days Before Ever Putting A Pending Code in P0122 Throttle Position Sensor (Curcuit Low) Is Usally The First Code To Come Up But Not Allways It Has Been Changed And It Still Does It And Everytime It Throws Codes It Throws Differant Codes Under TPS Code But It Does Not Always Throw TPS This Morning It Was The Worst It Would Not Even Idle Right Then It Died After It Died Run Test And TPS Was One Of The Codes Along With A Few Other Code I Erased The codes And Restarted The Truck And Rechecked For DTS Codes And The Only Pending Code That Came Up That Time was P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Imput I Erased Codes Again And Now It Dont Show Anymore Codes For Now And It Runs Good Till Next Time It Does It Again Im Out Of Ideas We Cant Change Everything That Comes Up In Code Besides The Fact They Are Random And Never Come Up Same Codes In A Row
Thanks Jeremy

Update The Day This Was Writen It Went The Whole Day After Codes Was Erased And Ran Great I Checked For New Codes After It Came Off The Route For The Day And Still No New Codes But It Will Throw Codes Again Probaly The Next Time Out This Is What I Cant Figure Out About THis Truck if Something Was Wrong I Would Think It Would Show Codes All The Time And Run Bad All The Time But It Dont All I Have To Do Is Erase Codes And It Runs Great Till It Throws Codes Again