Last time I posted was about the knocking in my engine. Long story short, spun rod bearing in 110k mile engine (2004 2.0L unmodified WRX) warranted replacement. So I just got this (supposedly stock) replacement (55k mile) engine (and turbo) put in by a mechanic and the car is driving great, but it feels a little bit different.
The first thing I noticed was I could hear the turbo spooling, which I thought was odd, since I never heard that in the old engine. I think it is spooling up sooner, around 2400-2500 RPM, which is why I think I can hear it - the engine noise at the normal 2700RPM starts to drown it.
The second thing I noticed was considerably less mileage per gallon. I was getting an average of 25 MPG on the original engine and now I think I'm getting about 20 MPG. I think I have to try a few more fill-ups to know for sure, since it's possible I could be getting a wrong measure, but I don't think so.
From a more anecdotal perspective, I definitely notice more pep in the 2500-3500 RPM range and considerably less turbo lag, but don't notice anything different in the lower engine range. So my question is, was this engine or turbo modified in some non-obvious way (I don't think a engine can really be modified without it being obvious, right?), could it be a 2.5L engine (can that even fit easily?) or is there something else going on?
It's not really the worst thing in the world since it drives well and turbo lag is gone, but the lag never bothered me and I'd expect a lot more performance for a 5MPG cost. Any thoughts/suggestions would be helpful.