jap-sti-555

hi need a little advice about an issue i have with my scoob.
problem is it failed its mot last week for emissions (4.17%).
i have put a few additives thro inc cataclean (expensive), and am going to use octane boost pills when i take for retest, hopojng this will help.
i have also been having the engine check light come on when mainly i drive on motorways or boot it hard, took it for diagnostics and was told the lambda was faulty. i have today changed the lambda which cost me a shocking £209.
i have my retest tomorrow and am not convinced it will get thro. i have a decat exhaust but the main downpipe cat remains. will this make a difference? any thing else i can do to make sure i get it thro the emissions test ok? its my last day to get it thro tomorrow. and advice or ideas will be very helpful to me.
thanks for your time folks!

Turbotits

iTrader: (2)

if the lamda was faulty, the fueling could have been all over the place. So its a likely bet its gonna be better now. Immisions will be lower with two cat obviously. But it should pass with just the one in without a problem

Shark Man

It's likely the sensor will have been the problem. But for your best chances -after replacement the ECU should be reset and the car given a good drive (not hard, just a good run at 3000rpm+ ) to remove any fouling that has built up on the spark plugs and combustion chambers.