Usually an opening after the filter creates a louder more aggressive engine tone! If you've got this are you sure its not psychological?
When I fitted my stainless exhaust and k&n filter, it sounded alot more sporty, and I was convinced my 0-60 mph time was improved too (definitely felt faster) but when I did a standing start between 2 sets of traffic lights (which previously from green light on the first set foot to the floor I could just make the second set 250/300 yards away as they turn amber then red) Turns out there was no difference!

 

I know what you mean but no, it's definitely more HP and no more noise. Comes on much harder at about 2200rpm and continues through the rev range. The marker at the bottom of my road used to be difficult to reach 87klms after the T intersection, now it's easy to make 95klms (100klm limit)

The only other thing I can think of is that it's always been restricted somehow and this is normal ? I did used to get angry about how gutless it was.

 

Is it possible it was just the old filter was heavily clogged?

 

It was, I do a bit of sand driving and the dust from the sand fills the filter quicker than normal. Around 5-8,000ks (depending on how much sand work I do and if it is wet etc...) it will start to blow some black smoke so I replace it. The air filter change is on an "as needed" cycle which is different to oil changes and I replace based on smoke. This time was no different.

The speed test up my street never changes, I have never been able to get better than 87/88klms and I try, now I can do 95. I've owned the car from new and live at the same place as well so whatever was happening has been from new, that makes it more likely to be over boosting I suppose.

If it is over-boosting I should replace the part but if it is just better breathing I should replace the air cleaner with a better aftermarket set up.

Has anyone fitted a good aftermarket air cleaner and noticed a big difference.

 

I can't see why a crack around the air filter would affect the waste gate (I am assuming you have a D22 with a waste gate here)

If you do a lot of dusty driving it would be worth fitting a snorkel to raise the air intake and get cleaner air.

 

I don't really know how the wastegate is triggered, I thought maybe on vacuum and if this has changed somehow ? I can't see anything obvious like broken or disconnected.

P.S. yes D22

 

As far as I know the D22 had a simple waste gate, certainly it did before 2005.