Traffic crosses VLANs in this device
Since you are using vlans, you probably don't need to do this. Just do the firewalling at the point that traffic crosses vlans - unless you need security between lan devices in the same vlan.
Definitely but what could it be? I have tested everything what has been suggested but nothing helpsSo I guess you have something in your config inhibiting performance.
For me, it looks quite confusing wiki page...In case you are using a CRS1xx/CRS2xx series device: