Car dies after 15 mins of operation

[Juvet]

Hi,
I'm new here but have an issue with my 1996 FTO GR DOHC. The car has been in storage for a couple of years but is now out and running again. However, it runs fine for 15 mins or so then loses power and starts pinging really badly and eventually dies, leave it to cool down and the process can be repeated. Starts, drives fine for 1 -20 mins and then dies.
Replaced all HT leads spark plugs and one faulty coil pack, also checked Cat Converter (clean as a whistle), no error codes when checking ECU....
Any Ideas?