Hyundai Repair: 2001 Accent poor performance, quality plugs, secondary ignition

Question
My Accent currently has 115300 miles. Whenever I drive in town it surges or sputters when accelerating. At highways speeds if you are attemting to merge onto or climb hills you can feel it surging. I've had the timing belt replaced (broke twice) the coil replaced at 76k, new plugs and wires recently, new fuel filter, k&n drop in is clean, and did several fuel condition treatments to no avail. Any help would be appreciated. It does idle great and still pulling down high mpg's (38 hwy 30 city) thanks in advance!

Answer
You could have a problem with insufficient fuel pressure (requiring a new fuel pump) or with the secondary ignition system.  Mostly, the "sputtering" description makes it sound like an ignition issue.  If you've installed poor quality plugs or wires, that could be the issue.  Similarly, your ignition coil could have an issue as well.  

Is your check engine lamp on?  If so, read the trouble codes.  The trouble code(s) will likely give insight to the nature of the problem.  Follow up with the code number and I'll give you the next step of diagnosing the cause of the code.

If the check engine lamp is not on, I'm going to suggest taking the vehicle to a shop well-respected in driveability or engine performance diagnostic work.  You don't necessarily need to have it repaired there, but we're at the point where investing a small amount of money for diagnosis may save you a significant amount of money from not guessing at the problem.  Unfortunately, being able to feel the problem is very critical in ascertaining the possible causes, and I'm simply not able to do that over the internet.