Subaru Repair: 99 outback 2.5 dohc, hydraulic lifters, compression check

Question
I have a really annoying rough run condition with my outback. i have changed the spk plugs wires and done a compression check and all cylinders were 130 or better. I also replaced the injectors and fuel filter. So ia have been told that it must be tight valves, but aren't these engines hydraulic lifters. Are there any real common issues that cause a rough running condition at all rpm's. Thanks in advance fopr any help.

Answer
The Subaru 2.5l mentioned, uses mechanical lash adjusters for the valvetrain, this started in mid year 1996 to present.  

As far as why it is running roughly there are a lot of possibilities, has a vacuum gauge been hooked up to the car or is the tight valve thing just a guess?

Is the check engine light on or flashing?