[Fot] DCOE questions for Spitfire

[f s]

I have a DCOE 40 on my 79 spitfire. The engine is 9 to 1 compression. Mild
cam, ported and relieved head, balanced, very lite rods, flat top pistons,
Electric fuel pump, electronic ignition and a vacum retard distributor.  It
runs ok.... but does not idle well and seems like it has a miss at mid range
rpms. 2500 to 3500 rpms.  It also wants to run at 20 degrees before top dead
center, I would think it would run better and idle smooth at 1000 rpms. But it
does not. I have tried several different jet and air correctors and tried
several timing settings.  Does anyone have experience with DCOE 40 on warmed
over Spitfire 1500 engines.
Thanks
Andy