Hi Kathy, I for one (with the exception of Diesel engines), do not like a turbo/supercharged engine for daily driving..... regardless of what the oem manuals say, turbos beat the crap out of the oil....so IMHO, forget the 5-7K oil change intervals...along with most of the other extended service schedules as well. Although the design & engineering is excellent, the complexity of the engine and it electronic engine management systems is "Huge"...… meaning when things work right they are great, when they don't failure typically occurs and it is typically very, very expensive....ie. catastrophic level damage.
Gas mileage, well, in "theory" it should be wonderful but in reality, when you compare driver to driver to vehicle to vehicle in the same driving conditions, a normally aspirated engine will most always get better gas mileage than a boosted one....the only exception would be highway conditions where you have the cruise control engaged......but the increased mpg would be 1-2 mpg in most cases.
With regards to the intake manifold being plastic, yes, very true, and back in 1997 that is when they had a lot of failures caused in part by them merging aluminum and plastic together....that didn't work out all that well. Every engine mfg today has plastic intakes (including many high end supercars)...so you really can't get away from them..... but there really isn't a need to run from them either as they are very dependable, few have issues but they are considered a "disposable/repairable component"... but they are designed to be repaired easily....the o-ring gaskets that seal them up are usually the issue...and the o-ring assembly is a replaced part..... and not that bad of a job.
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Certified backyard mechanic I & II