The problem most often with K&N type filters is if they're oiled. After the first cleaning, all too often people put too much oil on them, thinking they need to saturate them. This causes particles of oil to make their way onto the MAF sensor, which screws up the readings it gives to the ECU, which in turn changes the air to fuel mixture which causes engine problems. Lotus has stated in writing that will void the warranty. I've used K&N filters in the past, and never had problems with them, but that wasn't on cars that cost $100k.
If you're going to just replace the stock filter with a new element, go with one that doesn't require oiling.