A customer contacted us as engine refused to run.
He had it towed over and we analyzed the OBD-II data and then yanked the valve covers to find two 3rd party valve springs broken and other springs too weak as the top of the valve stems were beat up

Customer had bought this 1998 coupe few months ago and it was clear the car was supercharged in the past and the fact the threaded holes for the rockers went right through the heads to be exposed to the cylinders that the heads had been ported.

Customer bought the springs, keepers, retainers and keys from Crane CAM and we used the spring tool of their's that clamps down over both springs for 1 cylinder.
The tool is not perfect but much better then the single spring tool, esp as we did this with heads still on engine as seen on far right of image below

Notice in other image the tops of valve stems on a few beat up and the spring 2nd from right is broke