I changed the camshaft position sensor today with a new Bosch item - no improvement.

To recap:

car starts and runs for 2 - 4 seconds before shutting down. It does this again and again.

there are no current trouble codes

fuel filter has been replaced with new Bosch unit

relay control module has been replaced with new Mercedes unit

fuel pressure is good

cleaned the MAF

cleaned and reconnected the contacts on the PCM. No corrosion

crank position sensor and camshaft position sensor have been replaced with new Bosch units

trying to find a way to check for plugged cat/ exhaust, but think I’m going to have to unbolt the cats to test for this

any more suggestions PLEEEEEASE anyone?