Elantra No low down power

I'm reposting this from the Elantra forum, to see if I get any reponse
 

My 97 elantra with about 100k miles has become really lazy out of the blocks in about the last 5000 miles. Sometimes it gets so bad that acceleration to 15-20 mph can take up to about 10 seconds. Once it reaches that speed acceleration is much the same as before. Unlike some of the other similar problems I've read where this happens when the engine is cold, Mine only happens when the engine is hot, and usually when its a fairly hot day.

I recently changed the plugs, plug wires, air and fuel filers, all to no avail. It almost feels as though the spark is not advancing until certain revs are reached. There are no codes.

Anyone have any ideas

Are you getting any Check Engine Light codes?  My guess is that one of the sensors is bad.  If you to http://www.hmaservice.com you can check to see if there are troubleshooting instructions that could help.  (I've written up instructions on how to register and navigate Hyundai's site at http://www.dfwhyundais.com/diy/DIY-WebTechGuide.html)

Thanks for the reply. No I'm getting no DTC codes at all. Check engine light is off. Thats the most frustrating thing about this.

Is the transmission shifting, or is it sluggish because it is starting out in, say, 3rd gear?