RE: Plenum removal
The 2x2 box is the connector for the injectors. I just did this on my 2000 blazer. mine had a connector lock tab the needed to be pulled out first. Then I used a screwdriver to unlatch the two tabs that lock the connector, one on driverside and one on passenger side. The connector should pull up and off after the locking tabs are released. The hard fuel lines will pull up and out also, but you need to follow the lines to the back of the motor. There is a bracket bolted to the block that holds them in place that is connected to the lines. Remove the bolt and it will free up the lines enough to move them out of the way. Take the bracket that holds the lines into the plenum off and the lines will pull up and you can muscle them to the driver side. They won't stay, but when you inbolt the plenum, you can move them over as you lift it off.
When you lift off the plenum, the injector/regulator assembly stays on the intake. The plenum has a gasket that seal around the assembly and will lift off. Ipressed on the injector assy while lifting the plenum and it popped out.
Another thing is the main harness that goes accross the motor can be pulled forward so you can lift the plenum straight up. The first time I tried to snake the plenum out from under it. The second timewas alot easier.