If it's a 1.0L then it's perfectly normal for it to smell gassy, they don't burn all their fuel like the 1.2's do. The keen starting and and high revs on cold are a sign of a perfectly adjusted choke, and you are actually supposed to dab the gas pedal to knock the choke off pretty much straight after starting (about 5secs after).
Things to check;
Check that the air filter is clean, k10's tend to be a bit fussy about those. If the filter aint nice and clean the motor will feel a little chocked up and your fuel economy will start to plummet.
Vaccum Lines. Check them for cracks, splits or leaks. Especially the bi-metal valve line (conneting to the bottom driver's side of airbox), a leak there can cause unstable iding and hesitation when pulling away from a stop.
Generally though, if it runs fine and isn't guzzling fuel then i would honestly leave it well alone. As i said it's perfectly normal for 1.0L's to smell rich and gassy, that's how they run, they don't have cats to alter the emmisions (only some 1.2's had cats; SLX, Super S & special order models). Doing unnessasery work on a perfectly fine K10 is like opening pandora's box, i can tell you that as someone who opened that box many years ago.
The egg smell that pollyp mentioned is caused by a high level of sulphur in the exhuast gas. Which is caused by using poor quality fuel, or by using old fuel (i.e it's been sitting in the tank for a month or so). This can be given off by cat and non-cat cars and has no known effect on the exhaust system. It can easily be cured by switching fuel brands and giving the car a good long cruise on the motorway at a nice steady 60-65 for around 30mins.
