How many miles?
Think mine went downhill around 45k then down again around 57k. Did numerous things all close together, firstly blanked off EGR was better after.
Cold air feeds into air box with decone, K&N panel filter fitted hardly noticeable. Just as a matter of interest i tried the cone back in yesterday, initial throttle response was there but totally died after 2.5k revs and like a heavy 1600cc car.
I had Benny change my cam chain figuring it was stretched throwing the cam timing on inlet and exhaust fractionally out, also had tech 2 learnt new crank positions etc- Car has never been as good prior since 3777 miles on clock, fsh for 4 years. Was a little noisy on no 1 cylinder/timing chain end easilly missed.
Ported the throttle and cleaned was a big underestimated improvement.
Another mod that greatly benefitted was precat removal, you will wonder why people leave them in.
Suspicious of the cat as well but skint.