I have a 95 v8 with the square filter box, I moved the abs pump closer to the abs modulator by about an inch and half, wedged compressor between filter and airbox. this allowed me to run a short hose to air tank as an auxiliary reservoir, I'm still running air suspension.
if you have a TDi, you don't need all emissions stuff specially charcoal canister on right fender well. I would remove charcoal canister, this frees lots of realty. if air tank is still on chassis now you can plumb to it and use extra air to air tires or other. tank does not hold enough air to run power tools for long, nor does the ARB compressor has the duty cycle to keep up with the air loss of using power tools. it will over heat and shut down.