My son is 3-1/2 today and I am having the exact same issues. Everyone puts in their 2 cents, but I started worrying about it so much, and my hubby was really yelling at our little guy, and guess what...he wouldn't go poop at all.....7 days later, we had to give him a glycerine suppository because he was under so much pressure... and got really sick and had a stomach ace so bad. Every child is different. It has only been a couple weeks, but when he poops, I clean it up, and call it a day. (It is just not worth it to me for him to get it on my time table - it needs to be on his own)...
(Although my little guy used to go poop on the toilet, don't know what the heck happenend, cuz' now he just doesn't. He did go pee yesterday, and accidentally went poop, so I made a big deal of it! Who knows. aarrggghhh, rough times!)
We have tried the matchbox, so when he does go, we do give him one, and he does love it though!
My little guy won't wear his underpants anymore either - just his diaper, but he never has pee accidents (for about 4 months or so), and he is dry about 50% of the time in the morning...we just put the same one back on (as long as it is clean).
And Diapers are the same things as pull ups in my opinion! Just when they go poop, it is easier to take a diaper off then a pull up, and when they go pee, a diaper is alittle harder to put on, but I mastered that one!!!
And just in my opinion, I don't get into that having your kid clean up the poop mess... they are not a dog that you could rub their nose in it...plus mine would probably have it all over their hands, and then if it doesn't get clean all the way, yuck...yeah, I don't like that one! ha! (At least for me).
Again, the matchbox cars were working "alittle". Keep trying, something will work.....
So weird, especially because my daughter was potty (and poop) trained by 2 by day, and 3 by night.... Everyone's different!!!!
Good luck to all!!!