Basically, follow the guys until you slip past them in the turn. Dont let off the gas, no matter what, and as soon as you pass get up high on the track (just inside the yellow line). You MUST stay there whenever you make your passes. (this is of course after you drive around the guys). This allows the guys behind you to get the best draft on you bc its where they always line up.
If you are running AT, as soon as you hit 165 feather the accelerator on/off/on/off/on so it downshifts without losing speed. (6th gear cant stay at 165 ive found, but 5th gear can).
If you make sure to stay just inside the yellow line, the first car behind you will draft off of you. As soon as he gets right on your ass, drive (left) down low to get out of his way (sometimes other guys will come up fast too). If they can pass you before youre within (give or take 150-200m) of the turn, let them pass as well.
Otherwise, starting drafting the guy(s) ahead of you and slingshot by them right as you get to the turn. If you do it right, youll be passing them in with a speed of about 171-173. As soon as you get by, make your way back to the yellow line and stay there. Get back into 5th gear when your car hits 165. They will eventually pass you on the straight, then draft them back.
You'll should notice that by the end of the 2nd turn on lap 2 youll see the guy ahead of you. Don't panic, youve still got pretty much to catch up, but bear in mind these laps are long. Do this again down the front stretch, and stay high in the turn. keep your line, the guys will pass you on the back straight.
Slingshot passed them, and then get low! Stay low until you are sure you can slipstream the lead car, he should be in reach by about the time your 2/3 of the way through the turn if you did all of this right. As soon as your in reach, go up the track and get behind him, slipstream by him, and youve completed mission 23!
Note: I took me 3 tries using this specific strategy. The first time I lost by 1.6 sec. the second time by .86- seconds. The third time I won by .2 sec. Just keep doing it, youll eventually get the jist of how to let them pass and pass them back.
The most important part is that you must not ket off the gas to let them catch up! (you can to downshift in AT). They must be able to pass you halfway through the straight and then you must pass them back at the turn with a speed of at least 171/2/3/4... much faster than this and you may have to slow down to let them pass... good luck. If you still cant get it, PM me and ill try to be more specific to figure what ure doing wrong.