Again,your 340 spine arrows are fine for your setup.Try turning your limbs down a bit,maybe 1 turn ,check tiller and give it a try.Most bows like to shoot a heavier spine out of the setup,especially if it is borderline between spines.Your 's is fine though.
Another thing to try as well is set 6 of your best arrows aside,put your desired broadhead on and spin test them.Now shoot into the target and see what happens.Did the arrow hit the desired location on the target,if not and say it hits a little to the left then turn the nock ever so slightly to the left and try another shot,is it better.Often times it can be the nock as the culprit.
Is your rest dropping fast enough? Any contact of fletching will definately rob you of your potential accuracy.
If all else fails,then the only thing I can reccomend is buying a few arrows in the 340 spine,or equivalent on other manufacteur's arrows and try them.
Make sure centershot is dead on,tiller,cam rotation,and nock placement is perfect---good luck and keep us updated.