Is this true for some cars?

[Faust]

Im a noob, but I like my car. Its a 95 Geo Prizm 1.6L DOHC... Its a snail compaired to most if not all of the cars on this site. I like the body, and I know the car pretty well for a beginner. I had a 91 before this one, and I like this year. Its the GSI model so no power nothing except for the engine... It gets pretty good speed for a DD, but no torque what so ever. Im going to get the 4AGZE or 4AGE swap, but its been a bitch to find online. I have to go to JDM Imports to find the one I want, and its not that expensive... So far Ive done almost a complete exhaust upgrade. Here are the details: 1.8L Option headers (2.25in 4/2/1) 2.25in custom piping all the way to the ehxaust (this was made in a custom exhaust shop, and I think its aluminum, shoulda just bought the piping online) I also have a magnaflow cat. The muffler is a Tsuda with a 3in outlet (its annoyingly loud too, I hate it) Now my question is this... I was told that sometimes an upgrade can actually decrease your performance substantially. Would this be true for my car? Its the three speed automatic. Apparently my model tranny is recommended among the newer models, Im almost afraid to do this swap because of it.

[alpine_aw11]

Nothing that ever came in a Geo would ever be better than a 4agze swap. When a swap actually decreases performance it's generally because of ergonometry/weight of the new motor, or unless it's just some douchebag who wants a K20 in his Supra or some shit. I highly doubt a 4a would throw the balance of your car off to the point where it would decrease performance, considering you're on stock suspension there's not a whole lot of performance to mess with anyway.

[Faust]

Thanks for the input, Im getting alot of my suspension parts for a corolla. They fit my car so... Tein Coilovers, sway bar set, lower arm bars for stiff, if I can find one, a rear strut bar... Still looking into the big brake and rear brake conversion, not sure if I can pull that off though. I wanna get my com upgraded too, maybe I can get some more speed from the switch?