Remair, the AI has these prewarmed engines. It's what we got atm. And like you noticed you have to wait for your engine to pass 25 degree mark before taking off.
Here's some tip to stay with formation.
1. First thing when you get into cockpit is to switch fuelcock on and give 20% throttle and hit I. After that you'll have time to zoom in/out and turn off mirror, check map etc.
2. You can speed up the time it takes to heat the engine by applying continous brakes while revving up some.
3. Switch on the boost cutout thingy that'll give u a tad more power.
4. When close to 25 degree mark rev up and take off at full power.
5. Immediately after airborne retract flaps/gear
6. stay level till you're at 160 mph then climb sustaining 160 mph (best climbrate) until you're level with the flightleader.
Tip 1: If you have the icons on then the flightleader is the one with an A at the end. Follow him and all is good. He will circle the base once.
Tip 2: If you got icons on on the map then you can see the flight path and can cut a corner if you're unable to catch up.
Reg. mix reset. Check the key assignment for mixture. Some keys can be assigned to many keys. Probably you have the same key set for mix and pitch/rads. I once had my zoom in key also assigned to pitch. Took me a while to figure out.
Have fun!