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'99 OBS
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Discussion Starter · #1 ·
So I just finished my first month of driving after my rebuild/swap and something's off.
Here's some background info - I bought a '99 OBS (Phase II EJ22) with a spun bearing. Found a '96 EJ22 shortblock (Phase I), swapped the Phase II heads and a few other items onto the shortblock, dropped it in, and fired it up.
The oddball combo actually works quite well. The only caveat I know of (thanks to Storm) is that I've effectively lowered my compression ratio (and power output) due to the different shape of the Phase I pistons in combination with the Phase II heads. Ok - background over - hope you're still with me.

Here's where it gets strange. I can't get better than 22 mpg out of this thing - and that's if I baby it. Highway, city, it doesn't matter. I know that's not that terrible in the big scheme of things, but I could get that kind of mileage out of my 230HP Volvo Wagon.
My friend's stock RS gets 25-29 mpg easy. What gives with my OBS? Is it the lack of power that's making it work harder to maintain decent acceleration? I can't figure it out. I'm not getting any CELs, the ECU has been reset...what else do I check?
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