So i have been brewing for 5 years now, started making extract beer and moved to all grain about 3 years ago. As sad as it is i never really took any readings didnt care just liked making beer. So about 8 months ago bought a refract. and started taking readings and notes. Here is my problem when i make low gravity beers I have no problem hitting my og but when it comes to high gravity beers I cant seem to hit my numbers. My system is two bayou classic kettles, I use one for a direct fire mashtun and the other iuse as a kettle. I started doing 90 min mashes to try to up my efifciency but when it come to high gravity beers it makes no difference. I have a march pump. I just need some advice on what i can do to increase my numbers. I hope this is enough info let me know if you need more.