According to the seller it's a mk3 golf VR6 engine.
But the seller is a tool and really doesn't know anything about the engine, the MR2 or anything else for that matter. He doesn't even know which model VR6 engine it is or even what year it is.
The VR6 engine is a great engine actually and very very tuneable for cheap prices.
Chips are available for $100 gaining you a 7400rpm redline and about 10hp up top. Camshafts are readily available from most makers in lots of configurations. There are loads of intake configurations available and even whole intake manifolds. Exhaust manifolds again readily available, even ones for turboing.
All in all it's actually a very good engine, revs nicely, has a sound track to die for and very easy to tune when it comes to it and we all know it always does
Too bad the seller is a tool cause I would have grabbed that with an offer of £300 and stuck it in a garage and periodically yet slowly finish it off.