Wizard catless manifolds are of course straight fit, with lambda bosses already on them.
But if you are unwilling to pay that amount of money, I would suggest buying some second hand CF2 exhaust manifolds (from GTV), which you would have to combine with downpipes for CF2 manifolds as well. Rear CF2 GTV manifold already has lambba boss, so you would have to add one lambda boss to the longer downpipe (it is not a big job, it just has to be welded in properly). There are also equal lenght downpipes availabe for GTV models (check thread in the GTV section called Peco equal lenght downpipes), you would need CF2 type in that case of course, or CF3 if you get Wizard manifolds.
It might be a bit hard to get your hands on CF2 GTV exhaust manifolds.
Since you are smelling fuel, are you sure there isn't a leak somewhere, which would disturb the lambda sensors?