I tuned up old faithful about a week ago and it was running like a really noisy watch; somethings changed. Around town it seems fine, but after a highway drive I get blips of the check engine light and when I slow down I get a series of surges (about eight) until it settles out at the normal rpm. The code indicates O2 sensor. That's brand new so I'm not inclined to think it's the problem. No loss in power or mileage. Valves were adjusted. Timing seems right on 12 degrees BTC. Vac hoses and gaskets seem tight. It's acting like it's hunting for the right mix of air-fuel. Also deceleration is extreme. Almost like a jake brake effect. Any ideas? I keep going back to the timing, but advancing or retarding it gives me pinging or sluggish acceleration. Would a faulty throttle position sensor cause this?