not being familiar with the 2.0L i can't be 100% sure of anything i am about to tell you, but from a general knowledge of engine operation and a personal mechanics standpoint i would say that it is blowing out compression, most likely through a valve as it is not a constant loss. Most likely cause would be some thing causing a valve to stick temporarily, it may be returning to the closed position from a tap from the top of the piston, if this engine is in fact interference design, or the lifter or valve spring finally causes it to retract. The most likely causes of a sticking valve on an overhead cam engine would be a problem with a hydraulic lifter assembly or the lifter bore in which it slides. Another couple possibilities involve the valve spring, valve stem, or if it happens to be like my 4horse B&S pressure washer motor, the valve seat breaking loose from where it should be, very unlikely in an automotive engine as quality control should be far tighter. Sadly all these possible problems would require the head to be removed from the engine, whether or not this is possible within-car i do not know, but either way it is a big enough job to undertake.
P.S. most of the issues stated would likely be due to top-end oil starvation, with the valve cover removed, removal of one camshaft bearing cap and inspection of the surfaces will be a tell tale sign of this. History of severely low oil usually means only one thing... Even more problems.
Hope i could help..
Cheers
