Anybody have problems after installing k/n air filter?

Have to be more specific,

did you install a cone or a drop in (factory replacement) filter?

what problems are you having?

Potential problems with installing a K&N filter is that the oil from the filter tends to coat the elements on the MAF sensor. Which causes driveability issues.

With over 5 years of K&N filtering in 5 of my own cars and more years of others' cars, I can say wholeheartedly that I've never had any issues with filter oil.

Air box stock replacement:
This does actually help, as I've noticed with the butt-dyno though I haven't empirically tested it. Advantages are that you get stickers and a filter you never have to replace. After 12K-mile filter replacements for 60K miles, you've just paid more than what it costs to buy one K&N, and the original K&N would still be fine whereas you'd have to put in your 6th $10+ filter. Plus, these are actually better. They're better with oil but worse without it as compared to paper filters, so re-oil them every 10K miles. One re-oiling kit costs $10 and lasts about 10 resprays.

Conical K&N filters
On this page, ZZ Performance states that using a conical filter provides better volumetric efficiency than an open tube. Being that a flat filter in a rectangular prism decreases volumetric efficiency, you do get truly more power out of your car with this filter. Plus, there'* the longevity thing as stated above.

I've heard that oil tale but I honestly think its from people over oiling their filters. I've never had problems with them.