Yup dropped gain to 30 and worked up, stopped at around 40 and now it is similar to the Prod box. I also ran
the filter check as advised by @abcd567 with the following results . Top one is the Prod box with a spider ant and Pro+, the bottom is FA Ant and Pro+
Heaps of noise at the 840 range on both. Interesting to note that the dev box with the FA ANT has less noise at the 940 range but more at the 1090. (both are on a Pro + dongle). Hopefully the additional FA filters on order help both systems.