Cessna 340 High Altitude Operations (Please Help)

Dear Colleagues.

My name is Stefano Rota. I am from Quito, Ecuador. I am a commercial pilot, I did all my flight school in ICARO FLIGHT ACADEMY www.learn2fly.aero here in Quito. Currently, i have a chance of flying as a PIC a Cessna 340 for a friend of mine, based here in Quito. I used to fly this as a copilot but I didnt know that much back then and last, I was just being an assistant for COMS etc.

Any way, the fact is this is an airplane which I am aware is not adequate for operating at this altitude (Takeoffs) and I want to get some things clear before we start. So if possible I would like to receive a few tips, from people who have operated C340 or similar C421, C414 at different elevations. The airplane is getting maintenance done in TAMIAMI and were gonna ferry the plane down with the instructor, and do a few flight here in the highland as the airplane handles totally different.

Quito, is the capital, airport based at 9,228 FT. Yes, you saw right, NINE THOUSAND FEET. Now. I have been reading the POH and the procedures and all, and I have a doubt. This C340 has two Continental 6 Cyliner 310HP engines. In my flight school we used to fly Cessna 172's with 210HP engines, and for example we used to reduce the mixture for startup, basically to ZERO. On the run up we would regulate it based on RPMS, etc, and in takeoff we would get 12gph. And then we would never touch it again.

NOW, on the 340, I was reading the manuals and the takeoff procedures say MIXTURE RICH. Now. I have some doubt. As we are taking off from 9 thousand feet I find it hard to believe the mixture needs to be rich! And based on my experience thats not right. The books don't say anything regarding high altitude takeoffs so Im lost. Is it correct to take this plane off with the mixtures rich regardless of the altitude? In the MAXIMUM CLIMB checklist you see the following

1. Power 2700 Full Throttle Below 20,000FT
2. Airspeed 108
3. Mixtures FULL RICH BELOW 20,000FT
LEAN AS REQUIRED ABOVE 20,000FT
........

This is the only LIST or thing I could see regarding Maximum Climbs etc, but I will keep on looking. So, whats your take on this guys? I believe id be killing my performance with the engines at that rate of fuel flow. But thats why I am asking. We used to take it off like that, we had a long takeoff roll, but it had a good rational climb. But tell me what you think

Thanks in advance, and please, let me know, and I will have more questions. Thank you.

Stefano Rota