Hesitation while driving at constant speed?? 88 d50

[BradMph]

correct, should be some springiness in it and like Camoit said just a few degrees turn.

Are you sure your getting hesitation also. Maybe that's the way the truck just runs like and your sensitive to it? The smog device stuff could be increasing the hesitation, Andy's idea sounds like a good fix if you can leave it removed and block all the smog ports without emissions test looking under your hood it might be a good idea later on trying.
when the truck is running stroll back to exhaust pipe and if the exhaust burns your eyes within a second or two your rich, too rich. If its just heat, should be ok. Don't breath the crap, just do a quick little eye test. You get worse exposure daily just breathing our polluted air. It's not the normal way to check mixture, but it can give you a quick answer.