omesohi

ok heres the deal, i have a 87 toyota 4runner all stock with a bigger turbo (garret t3/t4) no intercooler,when its cold up to half way on the temp gauge it runs like a bat out of hell,but as soon as it goes one bar over half way or hotter the yot falls on its face,no power at all wont even run. but if you let it sit to cool off for a little bit (10-20 mins)it starts back up and runs again. i have 125 comp. across all cyc. timing is good also,its killing me, dont know what to do but shoot it!!!! i need help bad.any clue anybody?