My 86 fj60 with 310k miles (I bought new and it's been very carefully maintained) sometimes stalls on steep, bumpy 4wd grades and sometimes on sharp turns. Rpms just drop to nothing. Sometimes starts right away, sometimes not. When it does start, sometimes idles rough for awhile, somtimes idles fine. Twice I've had to get it rolling downhill, then crank on it to get it to start. Altitude seems not to be a factor as it's happened in Denver, but I've also been as high as 13200 feet without it happening. Steep and very bumpy and/or sharp turns seem to cause it. This is a new issue as I've been driving many of these 4wd roads for years without this problem. Carb kit components installed by excellent independent Toyota mechanic I've used for years didn't help; fuel filter replaced; fuel pump good. Shaken all the wires/connections while it's running with no results. Any ideas? Thanks in advance to anyone who might be able to help.