I posted about this last week. I am on test, fina, and eq and my lower back pump is quite aggravating. On leg days is when it is at its worse and believe me it hurts. I will do 8 sets of squats and on about my 2nd or 3rd set I can't even stand up straight. You should have seen me by the time I finished my last set I looked like Quazzy Motto. I was walking to the leg extensions that were across the gym and halfway there I almost fell over and had to sit down immediately because the pump kept getting worse. I am fine like 1 hour later and it doesn't get to bad any other day. I have back tonight and deadlifts are last on the schedule so I will let you know if I made it through them or not. Just keep stretching and and drinking plenty of water as it might help a little. The pain is a bitch but it's well worth it.