I have a Mares Abyss and I like it,( I know here come the comments), but I have a questions regarding adjustment of the air flow. I usually get a slight headache after a dive, but respect the ascent rates and always do a safety stop. I was speaking to a guy after my last dive and he said maybe I am not getting enough O2. I have had the reg into the shop since I first got it, is there a possibility that there is an adjustment and it is turned too tight?