I've finally found the cause my Cupra's hesitation during acceleration - a leaking hose that goes from the T joint (with the PCV) to the underneath of the intake manifold.
I noticed 'stupots_1982' earlier post with similar issues - his hose layout is different to mine, but that's probably because his is an R.
I've looked into 'catch can' and like the idea of vapours being collected but I just want a quick fix for now, so I've ordered Creationsmotorsport hose & new breather valve.
Got it back from the body shop after having both bumpers re sprayed and alloys refurbished in anthracite grey.
So from this
To this
Next mission. Wind deflectors and window tints.
Stage 2 mk1 lcr 260bhp