What size chain to use for Stihl 025?

Hello, that may seem like a odd question. But I just upgraded my 021 with a new 250 long block. So now it is a 025. The 21 used 3/8 lp chain and I see the 25 uses the .325. I'm running a 16" bar and will say with the new engine the saw really screams. Is there any reason that I need to change to the larger chain? I still have 4 or 5 good Stihl chains left in 3/8 lp but don't want to hurt the saw.
Thanks!

I've actually been dying to try some 3/8p on a MS250. Shouldn't hurt it to run the smaller chain but you can always take the rakers on the chain down a tad to slow the RPM's and take a bigger bite.