Re: High RPM bucking, hesitation
I have seen a lot of Buick 3800s do that and in each case it was secondary ignition (coil wires, coils, plugs) and it has half the number of plugs.
Key is that a secondary ignition problem like that will often only set a P030x (misfire) code while I would expect a fuel pump/regulator/injector to report an over lean condition (P017x).
ps electrical problems often surface with age and not mileage.