Emissions problem

Hi fellas. Just got major fail with emissions on MOT. I have a 2001 P38 4.0 V8 runs on LPG. Just replaced coil pack, ht leads, plugs, changed oil and filters and put on new cats and lambdas. It failed on petrol and was even worse on gas... Petrol 4.90 co level, 182 hoc level which was under. On LPG 6.90 co level, 2544 hc level , major fail. I'm at a loss, runs sweet on both petrol and gas.. Any ideas would be appreciated, currently pulling clumps of hair out..
Thanks for any ideas in advance..

Get more air in the mix ?

I would ask the same question here....

LPG Discussion Forum • Index page

Loads of people on there with RR and a few pro fitters. They might be able to tell you why it's worse on LPG over petrol, you'd expect it to be much less.

BTW if you present the vehicle for MOT testing on LPG they have to test on LPG. When you've got yours sorted it should have a much much much lower emissions reading on LPG. Some people remove the CATs entirely and if presented running on LPG the vehicle has to be tested to non-cat standards.

following up to what I put earlier, the law has changed.

Since January if a car was fitted with a cat when manufactured, it must still have one fitted or it's a fail simply because it isn't there, so you do now need cats for cars in LPG.