Alice is our 09 Justa Cooper with about 70k mi behind her. We were on our way on I-64 in WV, home to VA when she lost power climbing a hill, I checked things out and kept going on three cylinders. The only bad thing that I did to her was to fill her with 93 in a small town in the sticks of OH where they probably only sell 93 once a month. So I'm suspecting fouled up valves?? Any ideas?
I got home and replaced the spark plugs(they were pretty bad) which made no difference. I did a compression test and got 0 on cyl 1, 150PSI on 2, and 180PSI on cyl 3 and 4. I did a leakdown test without losing any pressure at all. After the leakdown test, cyl 1 has been pumping up between 45 and 60 PSI, but it still won't lose any pressure on a leakdown test. Any ideas what might be going on? I've run the rest of that small-town gas through now with SeaFoam and I'm working on a tank of Shell 93 with a can of SeaFoam but things aren't improving and sometimes I suspect cyl 2 is missing(judging from the occasional really rough idle and code on the Bavarian Tech program). The engine sounds as smooth as ever, so I'm hoping the cylinders are fine.
I took the valve cover off and everything looks nice there. Is a fouled valve the likely culprit? If so, here are my questions on which I'd highly appreciate any advice everyone would have:

What special tools will I need to pull the head and?

Any recommendations on the Koch camshaft tool vs an eBay generic?

Where is a good place to get the head studs and gaskets?

Here is a big one: What else should I do to the head while I have it off?
without spending a lot and how much would any recommended mods cost?

Any other advice anyone might have from having taken an N12 engine apart before. I've been into a few heavy diesel engines while I was growing up but no gas car engines like this.

A huge thanks for any help in advance!

 

Before I started self diagnosis and trial and error, I'd check for codes and also have MINI plug my key fob in to see if the computer spits anything out. Best of luck on figuring your problem out and fixing it.