Adding Extended Warranty to used car?

So I found a car I really like (08 e92 335 coupe) but it has a wastegate rattle, needs walnut blasting, and some other issues. The asking price is $15k and it has 65k miles so that's a good deal to me, but I would want to add on an extended warranty and I'm afraid it won't cover those issues if they eventually caused a problem.. Am I right..?? I've never bought an extended warranty so I'm not sure how in depth they go prior to purchasing it, if they would know about these prexisting conditions or not?



Thanks!