Well it has been a while since I looked, but...smoke test was done back in February and it was found that some of the PCV hoses were bad. Replaced those. Air intake tube was replaced when I bought the car a year ago, but it could be that it's come loose (or even cracked again as I live in a very dry climate).

Last time I pulled the DISA valve, it wasn't the valve / flapper itself that was bad, just the seal. The seal wasn't bad enough to replace it right then, but I think it is now, just based on symptoms. It'd be preventative maintenance more than anything. Will check it again soon.