Lots of speculation here, but let's cut through it. Please provide outputs from following commands:
fwaccel stat
fwaccel stats -s
grep -c ^processor /proc/cpuinfo
/sbin/cpuinfo
fw ctl affinity -l -r
sim affinity -l
netstat -ni
fw ctl multik stat
cpstat os -f multi_cpu -o 1
free -m
enabled_blades
You mentioned initially that you have URLF enabled but not APCL; you almost certainly need to optimize your URLF policy to keep LAN-speed traffic from getting inappropriately inspected in PXL. See my post here:
https://community.checkpoint.com/message/28972-re-layers-and-the-cleanup-rule?commentID=28972#commen...
--
Second Edition of my "Max Power" Firewall Book
Now Available at http://www.maxpowerfirewalls.com
Gateway Performance Optimization R81.20 Course
now available at maxpowerfirewalls.com