A few weeks back, I took my 2.0JTS out for a drive into town. When I arrived and switched off the engine, it "ran on" very roughly which surprised me as I only thought old cars would do this! I turned the key back on, the engine ran smooth again and turned off fine the second time. On the way home I was having a bit of fun with a Z3 down the dual carriageway but going round a roundabout it went into limp mode (very embarrassing) but as I want far from home I carried on. When I got back the engine was idling quite high (about 1500prm) and when I turned the car off there was an almighty bang from the engine and some smoke came out. It was so loud my neighbours all heard it. Anyway it was booked into Italia Speed for its annual service a few days later so we towed it there. They discovered that the inlet manifold had blown apart along the seam. Luckily they had a good secondhand one which they fitted (which also had a better throttle body attached) and the car runs beautifully once again. They could not establish why the inlet manifold had blown itself aparthowever. Any thoughts on why this might have happened?