2001 Cadillac SLS Missing and need sparkplugs changed

Do you hear the air pump(s) run when first started? Also check the vacuum solenoid that is under the top cover at the center of the rear bank. It has two vacuum lines going to it, and sometimes these lines come off. Has any repairs that involve frame removal been performed. Often times when the air pump connectors are disturbed, it results in a poor connection at the pump. Check the air pump maxi fuse(s) in the underhood fuse panel for being open.

The front bank is relatively straight forward. Remove the ignition coil(gray 8-10 bolts 10mm head). Remove the four boots(if you have a rubber tipped blow gun, insert it down the middle and apply pressure, they should pop right up), then the plugs. The rear bank is a bit more challenging due to the SAI check valve. I usually unbolt the bracket and solenoid, then I will remove the two nuts that hold the pipe at the manifold, the fresh air pipe comes loose from the bracket when the nut is loosened. Remove the coil bolts and it wil weasel out of the hole with some coaching. I have never tried it, but lowering the front of the frame might make it even easier. Then the boots, and the plugs.