by minus two bars you mean from all the way up? that is probably too much, try knocking it all the way down to 3 or 4 bars from the bottom (or left) you may be able to increase in certain areas. I check the sens by swingingover "clean" ground with no metal, very quickly back and forth a few times with the coil about two inches off the ground...you should hear no falsing. set it up another notch, repeat until you hear the falsing...then back it off that one bar and you should be good. if it starts to false just notch it down again, but I would never go lower than 3 bars...you will lose too much depth.
I almost always (99%) use 6 bars (factory default setting) sens to hunt. If you get into a trashy area or have a shallow target then back off to 2 or 3 bars to pinpoint the target. On my 250 I get aluminum cans hitting as dollar/quarter and show 2". If you lift the coil off the ground and swing about 4 inches above the target and still get a signal, it's most likely a can. Look for signals that DO NOT jump from coin to coin, these will be worth digging.