I'm not saying you didn't do it but ya some pics and numbers would be great, especially pics!! I would like to know what kind of power is coming out. I want to turbo my I4 Bu' just to get a little more power, maybe around what the V6 puts out but with better gas mileage. If it pushes 300 without any issues or crazy upgrades to drivetrain and what not then that would be perfect.
A turbo is going hurt your mileage (especially if you are going to attempt
to almost double your horsepower). Not to mention unless you really fine tune it (compression ratio, pistons, etc.) you;
1) will not see a significant boost in power
2) will see your mileage dive into the ground
3) will see unneeded wear and tear to your engine (especially if you are driving it hard)
If you want more power out of a Malibu, you are seriously better off trading in your I4 for the v6. Trying to make the I4 into a v6 is a complete waste of time and effort (time and effort that can be used to save up money to buy a v6) IMO and serious attempts to do so (through turbos, etc.) will only shorten the overall life of your current car.
At the end of the day, your I4 Malibu is still a family car built for comfort and competition with the Camry. Not a performance car. And attempting to run 252+ horses through only 4 cylinders (that were designed to handle only about 170) will only kill your engine faster.