OK, I'm going to spell it out for you. When your 4th gen 4Runner was designed, gas was well under $2.00/gallon, body on frame SUVs were king, and throttle response & instant acceleration were more important than fuel economy. When the 5th gen was designed, most of the SUV market had moved to CUVs, fuel economy was very important, and Toyota wasn't sure that they'd be able to move 19mpg rated BoF SUVs. In order to get the 22mpg rating under the new fuel efficiency test standards, Toyota had no option but improving the V6s power & torque to near the V8 levels and programming the ethrottle to essentially be lazy. That is why you V8 4th gen owners hop in a 5th gen and it feels slow. It won't immediately take off at part throttle because that is killer when it comes to fuel economy and Toyota programmed it to be as efficient as practical.
If you put the pedal to the floor in the 5th gen, it freaking moves. If you go part throttle, it is doing its best to conserve fuel and certainly does feel lazy... and that is fine for 95% of my driving. It isn't a racecar, afterall. Toyota didn't use magic to get 22mpg highway rating on the 5th gen versus the 17mpg highway rating on the 4th gen V8. They used common efficiency improving tactics (downsize the number of cylinders, decrease displacement, add dual VVT, change throttle tuning). The fact that it still has performance quite close to the V8 with the hammer down is quite impressive, IMO.
From AOL autos:
Compare Specifications 2009 Toyota 4Runner 2010 Toyota 4Runner
Exterior length 189.2 " 189.9 "
Exterior body width 75.2 " 75.2 "
Exterior height 71.1 " 71.5 "
Engine 4.7L V-8 4.0L V-6
Horsepower 260 @ 5,400 rpm 270 @ 5,600 rpm
torque 306 @ 3,400 rpm 278 @ 4,400 rpm
SAEJ1349 AUG2004 compliant std std
Fuel economy - city 14 mpg 17 mpg
Fuel economy - highway 17 mpg 22 mpg
0-60mph / 0-100kmh (s) 6.9 seconds 7.1 seconds
1/4 mile time 15.2 seconds 15.3 seconds
1/4 mile speed 89 mph 88 mph
OMG, the 5th gen is 0.2 seconds slower to 60 mph and runs the quarter 0.1seconds slower! It must be a total DAAWWWGGGG!