Get soda odor out of existing batch?

Gents,

My new corny keg had a really strong soda odor when I got it a few weeks ago. I soaked it in PBW and everything smelled fine. I put a finished Kolsch brew in it two weeks ago today and it's been carbing up since. I pulled a pint today to see how it's coming along and noticed that it has picked up a faint fruit punch scent, like the odor I thought I had gotten rid of. Not good.

I thought that my LHBS guy had replaced the gaskets, but apparently not. The lid o-ring still has a strong soda odor and I realize that I'll need to replace it and all of the other gaskets, but that doesn't help with my (potentially) ruined batch. Upon detecting the "contamination" I immediately hooked up my picnic tap to the spigot on my bottling bucket and transferred the beer into a "neutral" environment to at least prevent it from getting worse. I tasted it again and the odor/taste is definitely in the beer itself, not just the keg.

So, short of learning to like a sweet, fruit-punch flavored Kolsch, does anyone have any tips for getting rid of an odor like that?

Without raining on your parade, I'll regale you with a sad story of an early brew I did, I used A and W Rootbeer Bottles for a batch of beer... I washed the bottles twice, soaked them in Bakingsoda for three days. Washed them again in oxyclean...And no smell.
Well I bottled up my beer and three weeks later I opened one up and poured out a Belguim Double Rootbeer!
Even after all that cleaning and I could not detect any smell of rootbeer it came back to haunt me.
How bad is cross taste? if it's not too horrible maybe you could add some dry hops to the keg to either mask or enhance the perceived taste?

What I would try is bubbling CO2 through the beer out connect and then venting off the excess gas.
That might drive off some of the aroma. If it actually tastes like
soda it might not work as well.

Can't help you with the beer. But I had one keg that reeked of Mountain Dew (or at least that's what it smelled like to me). I put all new rubber in it, cleaned with all kinds of stuff. Finally filled it with water and baking soda and just forgot about it for a while before I ever decided to use it. That seemed to help.

Replace all the o rings including the dip tube o rings. Also take out the poppits and clean the springs. Soda gunk gets built up on them. Remove the dip tube and clean very well. Pbw has worked with real hot water to get rid of all the soda smell in my kegs.