Since the OP said he found his car pissing fuel AFTER going for a drive, in the interest of preventing another FC car-b-que, I'll mention that it's pretty easy to pressure test the fuel system after installing injectors but before you put the UIM & rest of the engine back together...
I know this is the case for S5 T2's & NA's but it probably applies to S4s as well. Look for a yellow 2 pin connector plug by the passenger side shock tower. Put a jumper across its 2 terminals, and switch the ignition to ON (not start, duh). You'll hear the fuel pump running, the fuel system pressurizes and you'll know quick if you have a leak. Here's the FSM section for more details:
