I have been fighting this problem for 6 monts with my 2001 TYrooper: truck runs fine then after a long run starts to miss and buck------had a bunch of Isuzu mechanics look at it, last time thay had the truck for three weeks....comes up random misfire codes on the OSBII ....so far this is what replaced:
1-Spark plugs with Denso's
2-Ion sensing module
5-Cleaned the EGR valve and passages
7-Checked and cleaned all connections, ran dianostic for both banks of cyl
7-And last but not Least the ECM/ECU
Also have been adding the Textron to the fuel.
So far nothing has made a difference..and it is costing me a small fortune...all parts are from Isuzu not junk of aftermarket..still having misfire , but only afer a long sustaned run , when cold not a whimper..All the Isuzu folks a re at loss...HELP !!!!!!