i wouldnt say stock pistons and rings are shit at all. theres loads of starlets running 100+bhp over their stock power out put from the factory, with some of these engines over 20 years old now. i ran a td05 setup for around 2 years with no issues ect. or look at mini valvers making 252bhp, that gets abuse every time its taken out, its seen 165mph a few times now too, last 1/4 mile day it did 25 runs maybe more no bother. something must have been wrong with your engine for it to fail all of a sudden on the rollers.