Hi

I bought my 1st Scooby in Sept 2015. It has a full decat exhaust system which unfortunately failed MOT emissions test!
The engine management light came on the day before MOT so thought I would put through MOT anyway & see what came up.
Emissions reading were as follows

Fast Idle Test
CO: 0.563 Fail
HC: 51 Pass
Lambda: 0.999 Pass

Second Fast Idle Test
CO: 0.672 Fail
HC: 44 Pass
Lambda: 0.992 Pass

Natural Idle Test
CO: 0.650 Fail

I had a scanner on to see the fault codes. 2 codes P1410 & P2433.
This suggested the secondary air intake pump & was advised from my local garage to take to Subaru specialist.
Booked into Subaru for diagnostic (£85) WOW!!! EXPENSIVE!!
They also suggested same fault. They stripped it down and found out that it was fine. They suggested replacing a relay which they have now done. Checked emissions test again & said it was still high. Also mentioned that having no cat was going to make a big difference & probably won't pass an MOT without one.
They have suggested having a pre-cat fitted at turbo end . The question that I would like answered is: is all my emissions trouble going to be resolved by having a pre-cat fitted & will it pass MOT after? It is obviously going to be an expensive job & I'm worried that I will spend a lot of money to not resolve the problem. With my Scooby at Subaru it is costing me a small fortune!! Up to £300 already & nothing fixed!!

Any help/advice will be appreciated. Thank You