Interesting, I've been looking at this one form Forge Motorsports;
https://www.forgemotorsport.co.uk/MQB_Chassis_VWAudiSeat_Mk7_GtiR_Leon_Cupra_280290_S3_8V_High_Flow_Inlet_Hose--product--1580.html
Same sort of product but manufactured in one piece with the hose, apparently these types of bolt on mods are good for 10% increase.
"Apparently" you are dreaming if you expect a turbo inlet will give anywhere near 10% power gains. 100$ or thereabouts spent in fuel are a far better investment for your car unless you're after the noise. All those piping upgrades esp. on these cars are waste of money unless as the very last mod on serious BT setups where a couple grand has already been spent already on the car and even then the gains are minimal. Lot of people confuse noise with power though so they keep having a market.
I’m not fully convinced either hence the use of the word ‘apparently’, that said the design is a major improvement so must have some effect, so I do plan to give it a go if nothing more the increased intake sound and reported improved throttle repsonce are both appealing.
Taken from the Forge Motorsports website;
The Forge Motorsport high flow intake hose for the MQB platform 2.0 engines, eliminates the highly restrictive plastic inlet pipe, and replaces it with our smooth bore multi-ply silicone hose which increases air flow, improving efficiency and performance. This equates to increases of up to 10hp which is a remarkable gain for an easy to fit bolt on modification.
Ok, I interpreted "apparently" as something which has been proven with solid data and from what I've seen, all those items offer minimal gains at the range of 2-3% and even then only on stage 2+ cars which have anyway upgraded the rest of intake and piping as well. Forge says 10hp but is it 10hp on a stock 230bhp GTI or 10hp on a stage 2 320-330bhp one? Quite different case. And of-course every tuner advertises their product as the best thing since sliced bread that makes you wonder how come doesn't everybody have it on their car. Even those values are close enough to the statistical error you can expect from a dyno so... That been said nothing comes close to the miserable gain/cost ratio of intakes so you can consider an inlet the better choice to spend your money on I guess.
I would avoid silicone hose solutions like Forge's though when for roughly £20 more you can get proper billet aluminium CNC machined ones from CTS, APR and Racingline.