my little frenchie farts up some nasty gasses
dont really know what to do and which food is best to stop him farting or at least stop them smelling so much
any help????

Is he still eating the cat food? :-)

I would avoid chicken based and anything too rich.  The Lamb varieties seem to be e less gassy, though the bull breeds seem to be prone to producing noxious farts ;)

Invest in nose pegs and those auto ambi air things to fight back the smell.  I have tried for many years and when you get a farter their is no stopping them. :-D

Emma