340 smoking bad

My 340 has learnt a new trick that I am NOT liking. It smokes while running and REALLY smokes when I get after it. I am going to do a compression test and leakdown test. Any thoughts as to what it might be. Both banks are smoking, but one worse than the other. I thought it might be valve seals as the motor sat for seven years before I got it. The oil pressure is real good if that helps. The motor seems to run really well, starts well and seems to still be making good power.