Latest version ECU flash
 

I have an 03 CTS with 41000. I bought from a friend a while ago.
How do I find out if I have latest factory flash for ECU?
I have a rough idle. I plugged my AutoEnginuity diagnostics into it and it keeps showing me current misfire on #2. As I am watching AE #2 misfire just clicks away to 255 in less than a min. ( I have the count set at 1 - 255 )
I replaced plugs with oem bosch, new coil pack, new intake gaskket kit, new orings on injectors. I even swapped inj. #2 with #5.
I still have a misfire on #2.
I am not getting any DTC's ( no check engine light ).
Dealer wants $110.00 to tell me if I have the latest or if they have to reflash.
I asked if he ran my vin.# if that would tell him what version and he no.
Any one know the latest version #?
and if dealer can check with just vin#?
Many thanks in advance.