'96 C280 Engine Issues (idle,throttle,acceleration). Help!!

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I own a '96 C280 with 120k miles and have recently been having a problem with the engine. Intermittently, the engine:

1) revs the RPM's while at a complete stop; or
2) cuts out during acceleration or at speed.

I've been searching the forum posts for the last several weeks and the general diagnosis for this type of problem is that it's the Engine Wiring Harness, Coil Packs, or MAF.

Since it appears to be the most common issue, I started with the Engine Wiring Harness. But, after checking the exposed sections of my harness it appears to be in pretty good shape (unlike the rotting/cracking pictures in other posts). I bought the car from a MB dealer in '98 with 30k miles on it, so the dealer may have already replaced the faulty harness.

Second, I replaced the spark plugs and cleaned the coils and MAF. Although this gave the car more pep, it doesn't appear to have cured the problem. Plus, I don't think it's a shorted coil pack since the car has a pretty smooth idle generally (other than problem #1).

I haven't been able to run a OBDII diagnostic test yet (not that those codes ever do me much good), but the only visually obvious engine issue is a leaky head gasket (leaking in the very front of the engine). Is it possible that the oil from the leaky head gasket is interfering with an electrical sensor (injectors or air)? Before changing the spark plugs I cleaned and degreased the engine so its pretty clean now but still has the same issues.

Please help. I'm fairly new to the DIY game, but can't fathom taking it to the dealer where they'll charge me more than the car is worth.

Thanks!!