I have a 2003 Evo and have never thrown a PO300 code even at close to 400 WHP. Now I built a new engine and removed the Balance shafts and added forged internals. Now I am getting the PO 300 code once and a while. I intentionally set up the engine a little loose so there is a little piston slap until it warms up. I am thinking that this is causing the PO300. Just wondering if anyone else has experienced this. I have done tons of logging and I am not picking up any real knock and it is not pulling timing. Thanks