After fitting a pipe and filter I'm very much doubting them now unless the cars had a very minimal stage 1 which I'm not contemplating at the moment. I can't understand why they are selling these DV'z if they cause problems as the big tuners sell them and don't mention anything regards losing power Not saying you don't know but I'm just shocked at this. My tt had mods Badger5 v3 tip, Cone filter FMIC relentless down pipe de cat cat back milltek de baffled charge pipe and no issues with power before a re map in fact a little bit throatier and after the remap it was very quick.
Gains on a stock map are minimal, often find you lose some low down torque and gain a small amount of top end HP. Only really worthwhile when remapped at a minimum. There are also good designs/intakes and bad ones, and the MAF housing size & diameter along with the MAF calibration in the software are critical for optimising performance and need to be matched.
Revo software for instance (and this is from experience) - When upgrading to Stage 2 software, I used the original MAF housing cut from the airbox, and as a result saw poor response/performance, high fuel trims (+15%!) and low MAF readings. Swapping to an aftermarket intake and MAF housing (same MAF housing diameter and sensor placement as the Revo intake) saw the car run much better. Even swapping from my current MAF pipe to that of another manufacturer (the Ramair kit which positions the sensor slightly differently) results in a big drop in performance. This is due to the MAF calibration being matched to their intake.
Why do 'big tuners'/companies do anything? To turn a profit. There is a gap in the market for people wanting the dump valve noise and they fill it, make it sound as good as possible to maximise sales and profit. Since when is any company 100% truthful about how good a product is? How often do you see those electric fans that go in your intake claim an extra 25hp? Or those fuel magnetiser things that go over the fuel pipe and claim to increase performance and fuel economy?
The difference with your TT is that you used the original MAF and MAF housing, so you'll see nothing but gains by removing restriction with the filter and TIP, the MAF reading and scaling would still be 100% correct