If it has 150 PSI, I probably would not change the top end. Having not run a 272xp, you will not miss the extra juice. If it ever starts to give you trouble, you can go to a 50mm 266xp top end that will bolt right on and have some more power. Right now you likely have a 48mm open-port top end. It will probably last forever. These saws have a two-piece ignition that is not uncommon to fail. Other than that, they're tough as nails. here is what I would check:
1. A/V mounts (there are 6) are usually cracked or broken. If they are too loose you'll end up with a hole in the fuel tank or engine.
2. Fuel line and filter. Easy to check and cheap to replace. If there is any question just replace it.
3. Air filter. I have seen some pretty wonky ones on these older saws. If there is any gunk in the carb bore, filter is not working well
4. Clutch side crank seal. While you have the clutch off changing the spring, look at the seal in there. It is very easy to change, since it is in the oil pump. If it looks hard, just replace.
5. Muffler. I have seen several of these with rusted mufflers. Stray exhaust WILL burn through the topcover in short order. Most of the white-tops are missing a louver or two over the muffler already.
Good luck, and congrats on a good saw. Post up some pics already!
