I've read about speed upgrades including ECU flashing, cold air intake additions, etc. Are there any suggestions on any in particular that have proven to work? I'm looking for modest gains; not anything major. Thanks for any suggestions.

 

for NA engines, performance mods are all about getting air through the engine. You can get some advantage through an ECU flash - which will advance the spark more but beyond that you need to open up the intake (ie cold air intakes or a KN free flow filter), open up the exhaust (larger downpipe, free flow cat/exhaust). You may be able to find some parts to adjust the cam timing - not sure if such a part is available for the 2.4i... Don't expect much out of an ECU flash for a non-Turbo however, they work great for turbos since it can add 25% more boost (ie airflow). After that, things get expensive (pistons, cams would be needed to add hp). What I'd do is start with the intake and exhaust, then do a full tune up - new wires, coils, plugs, quality synthetic oil. After that I'd work on wheels, suspension and brake upgrades to make your ride a more enjoyable drive.