I just bought a 290 of craigslist. The thing is very easy to start almost easier than my 250. It also has a pinging sound which I have read may be piston slap and I have been told to let it cool and then start it to see if I hear the ringing slowly go away. Also the bar I believe is bent. Everytime I start a cut the thing bogs down and I noticed that the cuts keep sweeping to the side the further I get through it. The guy who owned it never adjusted the oiler I think and it doesn't seem to be oiling too well. Is there a way to clean the oil tank and oiler in case it was just gunked up? If it's bad then I guess I have to buy a new one.
I have found that low compression makes Stihl saws really hard to start and stay lit. If it starts that easy you may have low compression... hang it by the starter cord and see how well it holds. If it has good compressin and starts easy, it may just be a good saw in tune. A 290 should have a really strong recoil on it. Like rip your wrist off type recoil.
The pinging sound is more likely to be the clutch and drum at idle... its the clutch randomly hitting the drum making the pings. Almost all Stihl saws that I have had do that. The 290 has an adjustible oiler. Pro feature. Just flip the saw over and on its belly there is a small hole. Inside that is a slot adjustable 'oil control bolt'. Adjujst the oiler with the small screwdriver to the wider position, and it will gush more oil for you.
As for odd cuts, do you have a .325 or a 3/8 standard chain? I have found that .325 does not cut straight on any saw I have had, and they tend to wander and pinch the bar in cuts. If that is the case, switch to 3/8 standard B&C and sprocket. While you are at it, flip to a rim style drum and sprocket drive from spur, and you will be better off for it (better chain life, far cheaper rim costs over time, also keeps the chain on better and makes chain tightening easier).
I ran a 20 inch 3/8 standard B&C on my 290 and that thing cut great. It will run an 18 or 20 inch 3/8 stgandard B&C just fine. Keep your chains tight and sharp, and it should not bog. If you are used to a 250, it should not bog nearly as much. Sounds like a crappy chain, or bar and chain to me. Or it may be low compression, and a tired saw. Hard to say from your description.