Help! I've owned this Euro 16V for several years, purchased @ 55K mile; now @ 125K miles, mostly highway. The car is eurospec to the best of my knowledge (no cat, no O2 sensor, no charcoal canister).

Since I've had the car, I have had an intermittant (worse now) problem with engine performance. At low rpm, under load the car sometimes stutters, and then "kicks in" when rpms get high enough. At high rpm I will get white smoke from tailpipe.

The fuel pump and filter are new; idle air mixture valve about 3 years old, cap and rotor are new (wire resistance checked out okay last year), the chain and tensioner were replaced about 2 years ago, water temp sensor new (comparing US vs euro models I've noticed there are 4 sensors clustered near water sensor at front of engine vs 3 on euro, and 2 air temp sensors on air box on the US model vs. 1 on the euro - ?)

Some observations: new spark plugs seem to help for a liitle while (few hundred to a few thousand miles), they appear to foul quickly (black carbon soot), oil accumulates in the low end of the air box (might this be getting sucked through the engine at high rpm?), the car seems to run better when it is raining (moisture in air apparently increasing apparent octane rating of fuel). I also notice a "stickiness" of the accelerator pedal when starting to depress it- I tried to lube linkages under hood, but might not have done a good job, or could this be coming from a sticky flapper itself? Also, do the injectors go bad?

I recently asked the dealer to "fix," and as far as I can get out of them they compression tested the engine and said it was "very high." They supposedly adjusted idle, and changed the plugs and charged a lot for that. The car runs the same.

Their explanation: "compression ratio too high for US fuel." I don't buy it; car runs the same on 92 or 93 or 94 octane, and the owners manual says to use MON 88, RON 98, so in US (RON + MON)/2 = 93. I have the manuals (plus 16V supplement) and can do some things myself and need some help!! I love the car but am at my wit's end! but before I start throwing parts at the car - which at least is better than spending money at the dealer to NOT diagnose the car, at least by throwing new parts in the car I have something to show for the money.......

Thanks for your help.