a Withdrawal-grade pressure when he can't
the unresolved Powerless Rage issues that the thing is now he’s gotten so he’s used to resolving them on a more or less nightly basis, so that being unable to be freely alone to be active with the Browning X444 or even a SteelSak during the 2216– 2226h. interval causes this pressure to build up like almost a Withdrawal-grade pressure.
Context
The substitute-compulsion has itself become a chemistry: deprived of his nightly kill because Green walks home with him, Lenz feels the unrelieved pressure build to "almost a Withdrawal-grade pressure," the very physiology of drug abstinence reconstituted around the new habit. The book makes the equivalence explicit — the compulsion, whatever its object, generates the same jonesing deprivation-state — which is the desire-mechanism the whole theme is anatomizing, a lever the organism will pull on schedule no matter what is wired to its other end.