A while ago my 89 300E with 265K on the clock needed a liitle perking up. It would idle ok but I could feel lots of misfiring/stumbling going on. Most throttle applications were fine, but WOT was horrible. It felt like so much fuel was being dumped it couldn't handle it and would actually be a LOT slower. 3/4 to 1/2 throttle worked best.

I replaced the cap, rotor, and spark plugs, and immediately it idled smoothly and revved almost instantly. The WOT problem was still mostly there however. A month later, we're back to the same problems- idle is mostly smooth but I fell lots of misfires/stumbles, WOT is terrible, and occasionally it stumbles a whooole lot (mainly when cold).

I do know:
-air meter flap moves fine and is generally clean
-spark plug wires look ok but the one going to the coil pack has a tear in the outer layer, exposing the nylon inner wrapping.
-fuel mileage is horrible, I'm lucky to get 270ish out of tank around town.

I don't know:
-if the coil pack is strong or not (I assume it's the original one)
-when the O2 sensor and fuel filter was last replaced
-if the fuel distributor has ever been checked/retuned

It drives fine otherwise, never cuts off, always starts, and I beat the crap out of it. I love this car, I just want it to smooth out! TIA