I’ve got a 2010 1.6 tdci Fiesta I was wonder what is the best option for either a panel filter or a cone filter and suggestions for each 

Fit a dry panel filter by Piper Cross.I pers did not want the oiled one as it could get the maff sensor covered in oil and prevent it reading correctly.

I have gone down the K&N route for the other half's 1.6 90ps, and can say it's really woken up the turbo, pickup is a heck of a lot better than the 'recently serviced and replaced' (yeah right...) standard filter. I'm terms of being oiled, I'm savvy enough to check it now and then, but have one on my Focus as well and haven't had any issues other than when it was dry and I had just swapped it over from my old car of 2 years and had rinsed it off and hadn't oiled it up (I drove a LOT around dusty work sites at this point) and I ended up with a mucky maf, but a quick squirt of cleaner on it and all was fine again - my Focus model is particularly well known for airflow and MAF issues anyway so I wasn't surprised.. Once oiled up again all has been perfect for me.

The fiesta panel I see as probably a bit more resilient to chucking oil around given it lays down and the air drawn is less than the focus. Completely your choice of course, but worth noting that you can pick them up for under £30 second hand in more than usable condition, and a recharge kit is around d £10-15 worst case too.

Will a filter actually make a difference? I changed my dirty(ish) paper filter to a K&N panel filter whilst on a rolling road on my previous car, (mk1 Skoda Fabia vRS diesel). It made a massive 1.1 BHP (0.5%) difference!!!

In saying that, I'm sure other manufactures are different. I was still glad I bought the Filter and was told might be a little more power gained when ECU learns to use the extra airflow.

9 hours ago, Jim H said:

Will a filter actually make a difference?

...

more power gained when ECU learns to use the extra airflow.

Very true, on many cars the differences can be quite negligible, in fact on some it can even have quite a negative impact on performance, a fair amount of Japanese cars suffer in this regard but that's more a sign of a better designed air intake system which is made very specifically for a particular engine and its map is very specific to working with certain air pressures.

In my experience, the higher flow rate gives me a lot more lower-mid to upper-mid responsiveness, to the point that the missus even asked me what I'd changed (She hates me messing with her brum.. 😇).

On the focus, ikostly get a lot more noise and I get a bit more top end, but overall I'd say it's a really close match for the paper one, if even having the paper one potentially be a little better off for it a tad lower down than the K&N. Unfortunately it's a lot of try it and see as many cars and driving.styles are very different.

Dynos can show a little change to power output, but overall the butt-dyno and general driving will help you feel exactly where is different for responsiveness, and its surprising how much of a difference that can be for such a small change on a graph.

 

As for the ECU, I've found that on the Focus, resetting it with Forscan when cha going filters helps the relearn process along some, as it gets a fresh set of numbers to work with rather than deeply set ones where a filter change is going to differ enough for it to throw a bit if a wobbler, and tell you something is up.. The joys of modern sensors on a car 🤔😅