I have a 94 Accord EX with problems.    
The engine runs rough when cruising at constant speed on the freeway and in town but goes away once you accelerate.  
Hard acceleration results in no vtec switchover.
Today attempting to pass a semi, the check engine light came on and the car was very sluggish when passing. However, the C.E.L. went off after restarting.
All I've done so far is replace the plugs, cap, and rotor.
I've got over 200K on the motor and it's painfully obvious I'm due for a rebuild but I'm just trying to make it long enough to afford a H22 swap.  

Could I have a vacuum leak?  I'm not that mechanically savvy so I have yet to get the compression tested or have the CEL code scanned.

Any help would be appreciated.