i work for a company that makes pistons, and isn't mahle. AE is not a crap make but.....

the ERST piston was originally suplied by mahle. i think they may have used a forged piston, i know ours are cast. but they should still be ok for the original application (not necessarily for a 20 psi monster tho).

on the subject of melted pistons, the max temp your piston should see if your petrol engine is correctly set up (and isn't a top fuel dragster) is about 300C, and aluminium melts at about 600 depending on the alloy.

as was pointed out earlier, these 'melted' pistons are invariably destroyed by detonation, not melting.