[MA70-3.0GT]

burning inside the exhaust and coming out under the hood... Have you got your exhaust disconnected or a big leak or something? if it's inside the exhaust the smoke can only come out where it exits. I'd suggest more likely oil on the outside of the exhaust, when the turbo oil line or the power steering hose leaks it blows back onto the downpipe when on the move IIRC.
Hard to truly diagnose noises without hearing in person so afraid I can't suggest any more than being 110% that all vac lines are connected (and not split/perished). I didn't change my injector seals when I replaced my HG and was fine but guess that depends on how bad they were to start, a more likely source of hissing in that area would be either the plenum or lower intake manifold leaking through either bad gaskets or loose bolts. (you know what a pig some of them are to get to!)

Oil smelling of fuel needs changed ASAP as it could be thinned out enough that running the motor will damage the main bearings etc.

this could either just be old really contaminated oil or possibly cold start injector is leaking badly, probably cause rough running too but change oil/filter & make sure no air/vac leaks first, along with calibrating your TPS and we'll go from there