There is not much inside the engine really so a compression test can be valuable. But sticking valves in the heads can be a bad thing. But I have never seen them stick enough to drown an engine out of power.
Few things though. Fuel delivery issue, air intake issue or timing issue. If the timing chain was replaced and its off, then there could be an issue. But I dont think that is too likely unless there are other issues. But its a thought.
There is a thing called an OVP relay. Its usually a 10 amp fuse under a cover along the back firewall. Driver side. Mines has a U.S. style fuse, not a euro type. If this goes I guess there can be some weird issues.
The fuel mixture could be way off. That can be adjusted, many threads on how to do that. But I would start with a new O2 sensor to be sure its not bad.
Really there are a lot of things that come to mind. As suggested it needs a good visual once over to look for anything obvious. Check for vacuum leaks, etc. Then move onto putting in new plugs just to be safe. After all they are cheap and when you remove the old, not the locations. The condition of the plugs can indicate certain issues. Wires, if original, are a good idea. The list can get pretty long/expensive. So start with the basics, move onto plugs, then sensors, blah blah....
