99 F150 Hesitation...

Hi - Have a '99 F150 Lariat, smaller Triton engine (4.8L) with 100K (just
turned last week), owned since new and never really had any issues and love
the truck.   However,  about 3 weeks ago a minor hesitation developed when
you give it gas (under load).  Idols fine but hesitates when going up a
hill, accelerating, or step on it at highway speeds.  (You can cruise at 65
without the hesitation, but if you give it gas it'll start).  No SES light,
and wires, plugs and fuel filter are only about 15K old.

 Now I did have a problem similar to this once before early last year, (15k
ago) that started with a SES light which was traced to a O2 sensor.  I
replaced that but no effect, so I changed plugs - again nothing until I
changed the wires and that fixed it.  The wires can't have gone bad again.
(In fact, on my Brother-in-laws's suggestion, I replaced them with original
Ford wires at $100 for the set, so they aren't some cheap after market
brand)  Any other suggestions on where to look?  Could it be coil/electircal
related again?  Anyone know if it's a common problem for the coil packs to
go?  Little short on cash so I can't afford to throw too much money at it,
so any help is appriciated!

Thanks,

Scott