from what I've learned if you have the cams and trans covered the rest are basically wear type items that any car will be susceptible to.
A couple things that are routinely pointed out are rusty brake lines and rusty strut towers.
The intake manifold runner control (imrc) can get gummed up especially on higher mileage cars. If it gets bad the butterflies will basically lock up and the little gears that control it will be damaged.
Mine was a mess when I opened it up to weld the cams. I spent at least a couple hrs cleaning that up.
If you're going about 20 and stomp it you should clearly hear and feel the secondaries open right around 3500 rpm. If you don't, the imrc isn't working. The cheap fix is just to wire it open which many people do as a low end (very slight) HP mod.
A/C can be problematic. When I bought mine it would work for a minute or two then stop -- a common problem as I discovered. Most (nearly all) of these cases can be remedied by disassembling the compressor clutch and taking out a shim. Not a difficult job, but a frustrating one.
strut condition. OEM sho struts are non-existent or very near it. I guess people are replacing badly worn ones with 2000+ taurus struts.
Brakes have been a pain for me. I had a lot of pulsation when I bought it. Put on new rotors and new ceramic (oem material) pads. Felt great for 3-4k then started pulsating again. Tried to get some help from the mfg - didn't work. Replaced them with a different brand - same result. Don't know what the deal is, I'm just going to live with it.
I haven't really had any other issues.
I got a few warnings from non SHO "car" people pre-purchase that this is a high maintenance vehicle, but having a fair amount of repair capability I decided to roll the dice.
I've put 12k on it since I bought it and haven't done anything more than I thought I'd need to do.
I'm REALLY enjoying driving it, even to work!