1990 Toyota 4Runner 4d 4wd Upper Plenum Removal
 

So I am going to be removing my upper plenum to fix a fuel leak, from the fuel pressure regulator. I was wondering if anybody had any tips, tricks, or suggestions for me.

As I think mholme is saying, the FPR DOES hit the plenum when you turn it. I might be willing to remove a scrap FPR by bending it, but I wouldn't want to risk breaking the replacement when I installed it. Your choice.

The first thing to do is get a scrap of paper and write intelligible notes about where every vacuum line goes. It's not hard, but your visual memory will be useless to get them back in the right place. There are those who claim they can 'fold" the plenum with all the lines connected; I just don't believe it. You'll need to drain out about 1/2 gallon of coolant; you remove two coolant lines at the TB.

The hardest part (for me) in removing the plenum is the approx 25mm hose in the aft right corner that goes to the PAIR. You'll find it MUCH easier to remove hoses of all types by using a hot air gun, or even a hair dryer. Just warm the rubber a bit; it will get much more flexible, and easier to remove (and less likely to damage it).

Don't remove ANY high pressure fuel connections; the pair of crush washers at each connection must be replaced each time. Cheaper than dirt, but only available from the dealer. You CAN remove the low pressure fuel return (just held with an ordinary spring clamp). The CSI can be pulled out of the plenum without disconnecting the fuel line.

I'd pick up a plenum gasket before-hand. If you've never removed the plenum, you'll probably tear the gasket in the process.
Like riding a bicycle, the first time is the hardest. After that, you'll be able to pop the plenum off in minutes.