Suddenly getting intermittent rough idle on 1987 4Runner 22RE, so started with a vacuum check. When I disconnect the vacuum hose at the Fuel Pressure Regulator there is no change to the rough idle, but when I plug the end of that vacuum hose with my finger, no more rough idle. Bad Fuel Pressure Regulator?

 

Maybe. Maybe not. It's hard to imagine your truck accelerating at all with a vacuum leak in the FPR. Why don't you just get a cheap vacuum pump/gauge and check it directly?

 

Good idea. I have one, somewhere.