Problems with O-320-D1A conversion

[RV-4 Rider]

I converted my O-320-D1A to an IO-320. It runs rich through the low and mid ranges (mag checks drop 200+ RPM and when I reduce the throttle to around 1400 RPM it pours out black smoke and will eventually quit; however if I lean the mixture back about 30-40% back it smoothes out and gets a good mag check). Then, back to mixture full rich, as I advance the throttle past 1/2, the engine leans out (EGT's rapidly rise to around 1500F and it starts to "pop"). I have sent the fuel servo to 3 different overhaul shops (SE Fuel systems - where I bought the comversion kit, API, and Rocky Mountain Aircraft Accessories) trying to correct the problems. Each time I get the servo back, it runs well during the first flight. Then, the next day it resumes the problems I have stated above.

The airplane has been down for over a year and I don't know what to do. Any help?

[mahlon_r]

It does sound like a servo problem but, I would hook a fuel pressure gauge into the line from the fuel pump to the servo and confirm you have proper fuel pressure to the servo when it is running badly. If the fuel pressure is around 20 to 25 psi all the time then I would find a shop that will take your servo, nozzles and flow divider and run them on an engine for you. They will be able to isolate and fix the problem then. The shop I work for, Teledyne Mattituck Services, can do this for you. Call me next week at 1-800-624-6680 ext.305 if you are interested. When you have sent the servo out in the past, have they found anything wrong with it and if so what was that? Is the same thing wrong and reoccurring each of the three times or do they say it flows properly and nothing is wrong every time you send it out?
Good Luck,
Mahlon