I've experienced a peculiar (and consistent) problem with every iFDG A318, 319 and 320 I've downloaded to date. I can only climb to the lower FL 200s before the aircraft experiences rapid speed loss, and I can never climb above flight level 240 to 260 without outright stalling. I've also tried climbing at a relatively lower rate as I climb (about 1000 ft /min starting around FL 180) and even that doesn't help any.
I essentially gave up a while back and blacklisted the iFDG 318/319/320s from my simulator due to this issue and the resulting habit of deleting all of them when they didn't work out, but I came across one just the other day that is too good to pass up regardless of the issue so now I'm only doing regional flights where a lower altitude cruise is feasible. I guess I could also do the longer range missions if I really wanted to but it would be relatively unrealistic to cruise so low for longer 319 flights.
Interestingly enough the iFDG A321s do not have this problem at all.
I'm just curious if anyone else has experienced this issue and what I could do to address it?