This is another old story...
Please check this screenshot below..

I have posted it here about
Mystery Bag Mulligan, where you can change the item you got from a Mystery Bag using 3 RPs!
Naaah, now they changed it to 1RP instead...
Still, the feature is not good, not worth it at all!
None of Mystery Bag item is worth it for the exchange of 1 RP.. So, let's just forget about this feature.... Skip it, please!

PS : Thanks for the screenshot, Pawel!
So we have this new feature on the Mystery Bag.. it called
Mystery Bag Mulligan!
According to Haider, Mulligan means "second chance" (yep, English is not our mother languange). Thanks, Haider!
With this feature, you can change the item you got to something else using 3 RPs! Here is the info..
It's really that simple. Next time you open a mystery bag and get something you may not need, just try your luck again and open another bag!

Hah! Another way to sell Reward Points!
I wanted to see the new feature.. I checked on the Message Center, but I couldn't find it!
This is the example when I open one Mystery Bag gift from my mafia..
Then I checked on the FaceBook request page.. I opened the Mystery Bag gift from the same person.. here is what I got!
Naaaah, then I sacrifice 3 RPs to change the Reinforced Door boost above into something new.. Taaarrraaa...

I got 1x Money Sock boost for 3 RPs!
What a lame feature... skip this feature, please!!!

Really not worth it!
Source : Mafia Wars official blog
http://blog.mafiawars.com/2010/11/mystery-bag-mulligan.html