My D3 was shimmed to 0.6mm (0.4 alu +0.2 copper) which is way too much.

The engine wouldn't make ANY power unless it was leaned out drastically. I stopped tuning when she was starting to detonate.

I then shimmed it like a Novarossi (0.4mm total for 30%) and now she makes power even when she's slightly rich.

Too less compression is Baaaad.