If it idles ok generally the engine will be OK, make sure it's treated to a nice new glow plug.

Start from factory settings for the engine again, and be careful not to run it too lean on the bottom, Picco engines really don't like having a lean bottom!

I'd suggest contacting DH Modelsport or any of the Hastings for the factory settings if you don't have them, I dunno if you're new to nitro engines but just make sure all the adjustments you make are very small, and that you're allowing the engine time to get up to temperature before tuning.