I had an Fai chain kit on for a couple of years and never had any problems with it
The thing that done it eventually was when i took head etc off to do new piston rings it was a little stretched but i think that was down to constantly running low on oil because of rings and the cam cover was not sealed properly so i was going through 5 litres of oil a week doing 5-600 miles a week
Because of the difference in price when i first bought it and the price of a new GM kit was only 20 quid, I would not have hesitated to buy another one
a few years back the difference in price between the two was about 60 quid and i was really stretching my budget to get the fai kit
But thats some bad luck with what has happened to you
