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Take the injectors out, split a liter of DOT4 brake fluid equally over all 4 cylinders, let it sit for 2 weeks, then put a rag over the engine and let the engine toll so the excess brake fluid gets thrown out. Install injectors back and start the engine. Let it warm up at idle (do not load the engine as brake fluid kills most lubricating capacities of engine oil) and once the engine is mildly warm, turn off the engine and change the oil.
Then with fresh oil, go to your neighbours farm and offer him to disk a field with a 15 foot disk, and give it hell for an hour or so.
We've revitalised compression in many engines this way, even an old Mercedes 280 that has been sitting for years.
yard tractors over here, usually get put in front of the slurry mixer in winter time to burn them clean. Too cold exhaust gases clog up the head passages, manifold and exhaust.