Your Idle Air Control valve (IAC), may be clogged, which can lead to top end speed retardants.
You can take a look at this website link that may help to direct you on the part and how to clean your (IAC) valve.
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〉 Answered on Feb 11th, 2010 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
Without being able to test the vehicle I would first suggest that you check for codes. This means that you need to have a scan tool attached by a technician. Check around, there are automotive stores, such as Advanced Auto, that will do this for free.
It's possible that there is an air mixture problem, MAF (mass air flow) sensor could have a problem, check your air filter or it could be that you are having a problem with your fuel pump.
I recommend that you have a technician do a diagnostic test on this vehicle. You may want to ride with them so that they understand the problem that you are feeling. Hope this helps.
〉 Answered on Feb 12th, 2010 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines