* Specific Camshaft: Different camshafts have vastly different profiles (duration, lift, lobe separation angle). A mild cam might add 10-15 hp, while an aggressive cam could add 20-40 hp (or even more, but potentially at the cost of drivability). You'll need to specify the exact camshaft being used.
* Magnaflow Exhaust System: The specific Magnaflow system matters. A cat-back system (replacing the muffler and tailpipes) will yield less gain than a full exhaust system (headers, mid-pipes, cat-back). A less restrictive system will yield more gains than a slightly more restrictive one. Expect gains in the 10-20 hp range, maybe a bit more depending on the existing restrictions in the exhaust.
* Other Modifications: Are there other modifications to your engine? If you've already got performance air intake, upgraded ignition, or other modifications, the gains from the cam and exhaust might be less significant (diminishing returns). Conversely, if your engine is otherwise stock, the gains will be more pronounced.
* Installation and Tuning: Proper installation and, importantly, tuning are crucial. An improperly installed camshaft or exhaust system can actually *reduce* horsepower. A custom tune on an engine management system (if applicable) is almost always necessary to maximize the gains from a camshaft upgrade.
In short: You might see a total increase somewhere in the 20-60 horsepower range, but this is a very broad estimate. To get a more accurate prediction, you should consult with a performance shop specializing in your car's model. They can consider your specific modifications and goals to give you a much more precise estimate.
