it also can be related to phonetsy.tsy, there are diffrent methods for IMEI and IMSI mods, but not many got released in public except iExtraX7's IMEI mod.
I attached the IMEI mod and an info .pdf, maybe it could be useful for you.
And no I am not going to patch the .dll/.tsy, it would take to much time.
If you want to patch an app notify me, that should be possible.