Ok so I took the plunge and sourced a set of used ,matched SLAEG X5355 CPU s, an BNIB Apple spec Radeon 5770 graphic card, and a BNIB 120 GB SSD. Following advice from the forum, I upgraded the firmware to 2,1 first, then installed the SSD into a spare HD bay. I did a clean install of LION using a new thumb drive onto the SSD leaving Snow leopard on the old HD,transferred over the rest of the HD drive contents bar SL and booted up. Everything working perfectly . Firmware showing up as 2,1 and recognising the two 5160 dual core CPU s. Next step installed the 5770 with no problems and again all running perfectly. Final stage removed the old 5160 s and installed the 5355 s. New artic 5 Silver thermal paste applied as directed . Reassembled and rebooted. Great all perfect, and now detecting the 5355 Quad cores. Very quite and lot faster. Have been running all week until today. Booted up and the fans kicked in on full speed ,sounds like a mini jet taking off. Checking the temps with Temperature monitor. CPU s running around 30 C and all looking good apart from one of the memory modules which was showing 129 C. All the rest of the memory showing 37-40 C. What could have happened? I have 16GB of Apple memory installed , 2GB in all eight slots , and have been running this from day one. All thoughts gratefully received.