vacuum questions

I'm about done with a 55' chevy pickup on a 86' suburban running gear. I used the brake boster and the 400 trans. I'm instaling a holley tbi and need to instal vacuum lines to the trans and brakes and a map senor. Can I put a tee in the intake and run one line to the brakes and run one line with a small tee to the map and the trans. the only thing I see is that when I use the brakes the map will see a vacuum being used and rich the fuel and the trans will see the same thing and down shift. Also I need to run a wire to a switched power sorce for the ecu, I put a painless wiring harness in. Any ideas will be helpful.

MAP should have it's own vacuum source from as close to the TBI as you can get. OEM used port on bottom of throttle body close to ignition coil. Are you using a stock intake?? If so, you should be able to utilize a vaccum tree on the intake (@ 8 O' Clock from the distributor). I think that these had a check valve before the brake vacuum canister. If you have to share vacuum, I'd share w/ brakes and transmission.
Power for the ECU... Can you plug in to a connection on your fuse box that is switched with the ignition switch? I'd be sure to fuse it. I don't know what you've got for an ECU, the '89 ECM uses 10 amp fuses for both the switched and constant power.