1. You are running the system at the high PG due to the ash build up inside the Charcoal Bed. this is mostly due to the Biomass Spec.
2. Due to the above your PN can't go higher because the bed full of ash therefore you are not running the system at full rated because the air to the gasifier was less, further more you will run the comb rotor more often to bring the PG down. Because of this the combustion and reduction process will get impact, leading to higher CO2 and lower Hot gas temperature. Again it is because of the Ash content.
3. If the Pn and Pg is low it could be due to other blockages or leakages on the system. But if the Pg high and Pn low it is because a blockages in your charcoal bed. This need to be correct first, than it is easy for you to take care the others issue which we belief not give so much impact to the system and performance