I have attached a link for the 91 B2200 vacuum diagram, it should be almost the same.
Mazdatrucking.com is a great resource with lots of info on repairs.
firing order is 1, 3, 4, 2 for a 86' B2000
The 86-89 B2000 put out 86 hp @ 4800 rpm and 120 ft-lbs @ 2800 rpm. See the attached link for additional specifications.
No fluid in the master cylinder
Yes, the 86-89 B2000 engine will bolt into the 86-93 B2200. There are two mounts that go from the engine to the transmission on either side, you'll need to transfer these from the B2200 engine onto the B2000 engine. You will also need to keep the lower radiator hose from the B2000. Mazdatrucking.com has additional information on engine swaps as well as forums.
I'm pretty sure it's 15 Gallons, I just bough an 86 B2000 and the specs online said 15 gallons.
The vacuum pull off for the choke on the carburetor may be bad or out of adjustment.
You can find the 1986 Chevrolet vacuum line diagram at most Chevrolet dealerships. The vacuum line diagram can also be found at most auto-parts stores.
The exhaust manifold and turbo from the 88-92 Mazda 626, MX-6, and Ford Probe turbo models will bolt onto the 86-93 B2000 and B2200. See the attached link for additional information.
Yes, it does have vacuum advance.
Engines for the 86-89 B2000 and 86-93 B2200 are bolt in swaps. The short block from the 1st gen Ford Probe, and the 88-92 626 and MX-6 is the same, just bolt on you're cylinder head and accessories. Although I believe the B2600i has the same engine mounts the bell housing does not match and is not easily swapped. Mazdatrucking.com has additional information
86
Perhaps a vacuum leak? Check power brake booster -one way valve check all vacuum lines