Hard start when warm

After 2 years of no problems, my 1999 Jetta TDI began starting hard. The battery was changed, to no avail. Next came the timing belt, lube, oil and filter, glow plugs and relay switch, another power relay switch, the 60,000 mile tune up, and finally the ejector pump has been changed. All I need is a new turbo and I'll have a new TDI with the same old problem......starts great when cold , but turns over and over when warm. Any suggestions? Two dealerships are stumped by this and I'm frustrated!

Replace the starter.

The warm engine has higher compression than a cold engine. This is harder work for the starter. A weak starter can't get a warm engine to turn fast enough for the ECM's liking.