  A quark model with general Yang-Mills $SU_3$ symmetry leads to fourth-order
field equations and linear confining potential. The confining gauge bosons
(`confions') are treated as off-mass-shell particles and their indefinite
energies are unobservable due to confinement. The ultraviolet divergence of the
model appears to be no worse than that of QCD by power counting. Explicit
calculations of the confion self-energy show that the usual Faddeev-Popov
ghosts are inadequate to restore gauge symmetry for gauge invariant Lagrangians
with higher order derivatives. `Computer experiments' with FeynCalc lead to a
simple empirical method to restore the gauge invariance of the second-order
confion self-energy with arbitrary gauge parameters. The approximate results of
third-order vertex corrections suggest that the confining model could be
asymptotically free.
