1) Try this:

Warm engine up.
Put in neutral, set brake.
Raise hood.
Wait for engine to stabilize, (you said it stabilizes after a bit...)
Now, yank oil cap off.
..If the engine surges and idles erratically, good.
...if the engine does not react to the yanking of the cap, you have a hell of a vacuum leak. Fix it.

2) No need to use the wrong fluid, Pentosin is available everywhere.

3) The only "tune up" you can do is: replace air filters, replace 12 plugs, replace 12 plug wires, and maybe replace the crank sensor. If the car is near 100,000 miles, I'd do that anyway. I was having misfire and O2 codes like crazy around 96,000 with my Graphite and I changed all 12 plugs/wires and ALL of the trouble went away. Car ran way better, too.