Re: hesitation under load
First, I gotta say it... do not rev the car in neutral close to redline! By all means, do it if you want to damage the engine... without a load on the engine the parts freely spin and too sudden of an RPM raise or drop can cause damage - the higher and faster the worse it can be on the engine. Newer vehicles are limited to 3000-4000rpm in neutral (or park) because of this. Rev limit depends on redline or fuel cutoff of course.
So, providing the gap on the plugs was correct when they were installed, the MAF as mentioned is one thing to check and clean. While you have the intake nearly off, it's wise to check and even clean the throttle body. Check the air filter and make sure no animals have made nests in the airbox.
The car hesitates like it won't shift properly? Or it's just very slow to rev even going downhill? If you haven't done a transmission service, it's now due. A dirty or faulty IAC can also cause grief. Cam position sensor is another possibility, especially with revving it in neutral!
With 61K, I doubt compression would be an issue, but check all the fluids, namely coolant and engine oil. If any look like chocolate milk then a bad head gasket is to blame. I say this only because I knew someone who had a 2000 Taurus and at a mere 26,000kms, the head gasket went...
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!