I fitted a simota filter a few weeks back and mines sounds the same below 2500 rpms then sounds different when on boost. pretty sure its fine. No errors logged or any driving problems experienced. Seems to do it more on cold starts.
Ummmm, no, I'm pretty sure that it's NOT fine.
How on earth is your car not running properly ever going to be fine? The OP is claiming that the A3 he's driving sounds like a Scooby - meaning running on 3. I've heard it myself when I've had coils go.
Misfires mean one of two things in this scenario. Too much fuel, or too much air. Too much fuel will cost you a bomb over a long period of time, and too much air is even worse, as will cause detonation and things like holes in pistons.
If it was OK before, and you've fitted this induction kit and now it's running like a bag of nails, something is VERY wrong.
Firstly, remove the ****** thing and put the air box back on. See how it runs then. If OK, then throw the induction kit in the bin.
Alot of these no name brand induction kits have a ludicrously small air filter element inside the casing, which is VERY restrictive to the engine. Air flow through a turbo engine is one thing you do not want to restrict. N/A cars it doesn't matter so much, but when the turbo is pulling air through the filter at (Based on your car if standard- 1.8 TQS 180 BHP) 144 G/S, you need something to accomodate that air flow, not make it as hard as possible for it to get through.
My advice is remove the thing and retest to make sure it is OK then. If so, invest in a good, free flowing induction kit, otherwise there will be potentially disastrous consequences.
You have been warned.