First, why do you need to remove the plenum? (mostly curiousity on my part)
I can't think of a 17mm bolt under the plenum with fuel behind it. (Doesn't mean there isn't one...) The plenum support is is like an upside down 'L', one end bolts on near the motor mount/starter brace, the middle supports the plenum on a pair of rubber isolated bolts and the other end bolts up under the intake near the engine. Are sure the bolt you loosened had fuel behind it and not coolant? Maybe there is a bolt under there that goes into the cooling system? The fuel rail is attached to the plenum by a bolt from underneath (smaller then 17mm I'm sure). But there shouldn't be any fuel behind that bolt.
I'm not sure about the motor mount. The ones I've seen were round.
I can't think of a 17mm bolt under the plenum with fuel behind it. (Doesn't mean there isn't one...) The plenum support is is like an upside down 'L', one end bolts on near the motor mount/starter brace, the middle supports the plenum on a pair of rubber isolated bolts and the other end bolts up under the intake near the engine. Are sure the bolt you loosened had fuel behind it and not coolant? Maybe there is a bolt under there that goes into the cooling system? The fuel rail is attached to the plenum by a bolt from underneath (smaller then 17mm I'm sure). But there shouldn't be any fuel behind that bolt.
I'm not sure about the motor mount. The ones I've seen were round.