My S25s had chrome cyls but a wrist pin keeper failed and ruined one. One was a keeper that just needed the piston/ring set.
What do you feel caused the failure? Such as; the keeper failure was not on me IMO (after 10 yrs I had no no complaints). The 2nd S25 I feel was on me due to working in 100+ degree weather or getting my oil mix off after 10 yrs. I used left over 50:1 from my boat and possibly d/n add the extra oil to make it 16:1 (the tint possibly threw me vs excessive oil).
Please attach a good close Picture of the bad piston. Hopefully someone has seen this and know the definite problem before it's damaged again. Approx how many years or hrs did you use the saw before the damage (w/o me looking back)?
Reasons for a Poulan Pro 430VS to burn a piston at ports (was my search)? I found some info below but doughty your piston looked like any of these (in the link).
Get a friend to post the picture and you will catch learn the process. I always find the Pics must be a reasonable size (1-2 qualities above email), like 1 meg or less vs the best your camera will take.
The idle issue might be a cable or connection issue.
Take a pic or pics of bad piston and idle adjusting issue showing cable connection and adj screw and plate (as much as possible in good clear Pics. Send them to a trusted friend to post attachments and someone will possibly spot issues.