The 8 spark plug head engine is hard to work on, also there were a few years that Ford did not drill out the squirter hole in the connecting rod, the bump was still there just no hole. It could scuff the pistons in cold weather . after ford realized the problem they started drilling the squirter again. Cat location problems. Ford had a few engines that had a burn off Cat in front of the turbo. A hard blast in a cold engine could crack ithe elements in the cat and the pieces would ruin a turbo. Also after a hard run with the turbo you should let the engine run at idle or light load to let the turbo cool down so you don't coke up the oil in the turbo. The Factory Turbo engines used stronger parts internally .