Someone should do a test next time they're at a rolling road.. one run with a NEW OEM unit.. one with a NEW ITG filter and see if the rollers can see any difference.
The school-boy mistake is to replace a manky old OEM filter with a spanking new aftermarket one.. surprise: the car runs better with a clean filter!
Rich
Redline did it with a ph1 172 and the panel filter made 2bhp more with performance panel filter over STD. The bmc closed induction kit lost 7bhp lol!
I fitted ITG to mine and noticed zero difference. It was a nightmare to clean too so swapped it for a K&N panel filter as they are easy to clean.