Syrup in flue pan

[sportfreak15]

So to start this year with homemade 2x4.5 oil drop flue rig we pumped our raw sap into the flue pan at 40*. Everything flowed as it was supposed to and would draw off syrup regularly. This Saturday we added a homemade preheater. 3/4" copper going back and forth every inch inside the hood. It came out great and sap now enters the float box at 185*. Now the problem starts, 370 gallons of 3.0 sap has been run since the preheater was added with only 4 gallons drawn off. All channels of the syrup pan and the flue pan appear to be the same color where before the flue pan was nearly clear. I know the syrup is in there and will have to come out eventually but wondering how something that should have helped seems to be doing the opposite.
What I think may be happening is the flue pan without the constant cooling from 40* sap is boiling more heavy and forcing the more concentrated to the back of the pan allowing the less concentrated to enter the syrup pan and syrup from the syrup pan to actually flow back into the flue pan. Syrup pan doesnt seem to be boiling as heavy as it used to either. Not sure if this has anything to do with more boil in the flues.
Possible fixes.. Check levelness of arch. Never did this just eye balled the sap level. Try a smaller nozzle to try to focus the heat more on the syrup pan.
Has anyone experienced something like this or have an idea of what may have changed on me?