Fixitsans thread has made interesting reading, and is potentially a nice cheap and cheerful fix, but if you run a drill through your DPF, then it won't filter particles.
The thinking is if your engine is working properly then there are hardly any particles to filter. The particulate filter isn't an MOT item and is unlikely to be any time soon. If it does come back in then yoiu have to have a working dpf.
If you only drill one hoile straight through you will still get filtering with some bypass, because even though the dpf face might be covered in soot it is still permeable and passes some exhaust gas and therefore you will have some filtering.
If the filter becomes an MOT item and you have had it deleted by a remap and fitting a bypass pipe...what then ? The good tuners are saying they offer free support for all future remaping so that's maybe not an issue at all.
Also, if you fit a bypass pipe you also lose the DOC catalyst in the front section of the DPF housing. If particulate filters become an MOT item as a result of an environmental emmissions improvement drive I would then also expect to have to refit a DOC catalyst too.
Having done the drilling, I wouldn't pay for a remap just to get the dpf deleted. Knowing that drilling won't cause engine codes I would have started with one single hole and then checked it to see how it felt. Having said that i would have probably kept on drilling more holes too
Now the dpf is free flowing, this morning was particularly cold and it started almost instantly and emmitted only a tiny puff of smoke which is typical of the oil which probably leaked down past the valves while it was stationary for 16 hours, and oil smoke is a killer for the DPF anyway so a DPF would suffer from having to pass oil smoke (The car has 133k miles on it)
The way I've been looking at it is that if you have a blocked dpf then it will never be much good for anything else anyway. if the MOT changes then looking at the way DPF prices have come down, to just £300 now, then they'll probably be even cheaper int he future.
If you're definitely looking to go beyond factory performance levels then a remap is the only way for that.
The simplest test for a blocked DPF is to undo the temperature sensor in the side of the DPF can with a 17mm spanner and see how forceful the exhaust gas comes out when the engine is revved to 2000rpm - if it just sounds like there's very little backpressure then drilling a hole might not make much difference. if it sounds like a burst airline even one 10mm hole would make a noticeable difference, judging by the testing I did. Remember to give the ECU a chance to relearn the new parameters but you'll feel a difference straight away for sure under those circumstances