OK, I have been doing some reasearch and came across this thread in the process. I just read on the toyota forums that the gasses from the exaust when mixed with the fuel cool the fuel charge. ^^ Hmmm. Still researching. I rebuilt my Probe and used Weisco pistions to increase the Compression. I'm having a heat build up problem(Not toasted pistions that I'm aware of) But concieveably if what I have read is true about the gases mixing to cool the charge, your piston may have been toasted by the EGR. Best thiing to do is, ask for the old part, and buy a vacume tester, and see if you can use the vacume to suck it open, and see how long it stays open. If it won't even suck open, then it's ruined, and you should look for possible tampering of the device. Maybe it carboned closed or somthing too. But from an independently reseached, Yeah it might be possible. Do some reaseach on engine theory and EGR theory. hmmm, why not ask .com or Howitworks.com. Going there now my self!
EGR Valves

It'S FRIGGING TRUE!!! All them Little grease Monkies out there telling you to take off the EGR are LIERS!! Leave that BItch on! And make sure it works right!! The Carbon Dioxied is a gas that helps cool the combustion chamber. I've also found this description in manuals. So, although this is hot exaust gas it's a cirtain gas that actualy helps stop pinking and would allow for more advance on the timing in summer months. Science is cool!

EGR Valves
EGR Valves
EGR Valves
EGR Valves

WHoa And at Exhaust gas recirculation - Wikipedia, the free encyclopedia TOO! It's true It's TRUE!