I would avoid the ebay chip sellers....most of them are worthless...and at best will hurt performance...and my own experience with this has reinforced that opinion...I got one that after three returns stil would not work and I gave up on the seller not wanting to send my original chip for him to use as a baseline to modify and cut my losses and called it a learning experience..I would stay with an established tuner....there are plenty.

A proper tuner will work with your car in conjunction with a widebandO2 sensor and a dyno making minute changes....

there is no one size fits all becasue you can take 3 cars just like yours and each one might respond differently due to wear and other changes.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche