Personally, I wouldn't drop in the Ecotec, and instead modify the existing Vibe, 130hp motor. Personally, coming from a guy who likes cars on both ends of the spectrum, the Toyota motor is better than Ecotec. No mod potential? Just take a look at the Celica aftermarket, and there'* your Vibe aftermarket... and I'm not referring to rice, I'm referring to real stuff
Wait a minute, doesn't the Vibe GT already come with the 180hp motor?
: You drove the 180hp version? If you did, it probably explains why you felt the lack of power. That motor, known at Toyota as the 2ZZ-GE, makes its power allllll the way up high, like how DOHC (not SOHC) VTEC Hondas work. You gotta rev it to do stuff. The 130hp motor, on the other hand, the 1ZZ-FE, makes a lot more power down low, and is more street-friendly. Slap a blower or turbo onto that, and you've got a really friendly engine around town.
The engines are of a Toyota design, but the high-spec motor was tuned by Yamaha. Since the Vibe was always based on the Matrix, it always had a Toyota motor. It was a joint-venture on GM and Toyota'* part. However, the two cars are made in seperate plants - the Vibe in the US and the Matrix in Canada. I've heard that Matrixes are better built than the Vibe overall