Firmware 8.0.2 vs 7.1.x IPSEC

I noticed after upgrading our Balance 380, 580,710 the following patterns persists:

a) Very slow IPSEC restarts on 8.02 ( disable tunnel, apply changes, enable tunnel, apply changes).

b) CPU utilization is typically 100% and holding whenever that happens. On 7.1x firmware, it is almost instantaneous and CPU spikes are much much lower and shorter duration ( <5s).

Is this an expected behaviour due to additional checking/validation on higher firmware versions?

I still have different units with different firmware around.