When looking at mods, one of the principal paths taken was the one around air intake. The restrictions present on the stock car had to be improved or better, eliminated.
So, different steps were taken, some more successful than others.

The first was to put on the stock filter case a free-flow panel filter, this one was K&N. I’m really not convinced that these filters are less restrictive, though...

As one of the biggest drawbacks of these filters is the oil media used to increase filtering capacity, oil particles soil the thin MAF wires and through this contamination can damage your car, as if the MAF doesn’t register correctly the air flow, you can run a lean engine and damage your pistons.

Nevertheless, this condition will make the MAF register incorrect values and the car to run erratic and not to its full potential.

One of the trials done was to install an open air filter kit, this one with a heat shield.

This was a very effective filter, lots of flow, but a few known drawbacks.

One was noise, you could hear clearly the whine of the turbine, the recirculation valve opening and closing, all giving to my taste an impression of a ricer car.
The other was that the filter still was an oil coated cotton media, having the same MAF sensor issues as the previous panel filter, so maintenance of the setup was increased to clean regularly the MAF sensor as the filter area is much bigger.

On the next phase, I decided to tackle the whole original intake system, and try to modify it to get rid of restrictions.
This had two main advantages:

1) Less noise from the original setup, compared to the open air filter.

2) Being able to use the original paper filter media, eliminating the MAF issues. It has been established that there are no real gains just by using an oil coated cotton media filter.

Also and added advantage was that maintaining the stock setup there were going to be less issues when passing the ITV (Emission Control Test), as anything non stock is always challenged by Inspectors.

The changes done also were to disconnect the tubing that went from the air filter box (5) to the resonator box (1), and this resonator was eliminated.

Here below you can see the resonator box.

The original air filter box was kept, but a big opening was done on its front side as you can see below, this in fact is an open air filter.
Here it’s still missing it’s water mesh, to prevent water entering the set-up.

The original, very narrow and restrictive rubber tube (6) from the MAF/Air filter to the turbo intake pipe (7) was removed and exchanged by a nice Speedparts one, only in blue though.

The turbo intake pipe was removed, as it was one of the most restrictive parts in the original setup, the bends and the internal size of this tube were impairing airflow heavily.
It was exchanged by this nice Cobra pipe that is stock in the 95 Aero from 2006. The advantage is it fits nicely (not much room to wiggle the bolts though) it’s a stock SAAB part and fits exactly to the TD04, the price is also great, as it only takes € 80,00 from your pocket.

Installation is somewhat difficult due to lack of space, it fits snugly, but no room for big tools, the advantage is that you will never remove it..

This last set-up has proven to be the best, the equilibrium of intake - exhaust looks to be optimal, the paper filter makes the setup worry free, just change the filter every 20,000 kms and go! No ricer filters to be seen, no unwanted noises and plenty of performance.