You have already mentioned some of the things that I'm going to list, but these are some mods that I would recommend for regular tracking and longevity.
1. Oil cooler
2. Inter-cooler and upgraded piping
3. Charge pipe
There's no radiator upgrade that's currently available on the market. The only work in progress that I know of right now is that ER is developing a radiator upgrade.
However, you have a 335IS, meaning you already have an auxiliary radiator upgrade.
Which brings me to the next point, due to the auxiliary radiator, you would only be able to install the single oil cooler upgrade from the ER sports edition oil cooler unless you mount the second oil cooler in front of the radiator or remove the auxiliary radiator.
ER also has a complete set for FMIC and charge pipe with upgraded piping which keeps your IAT down and improves your throttle response.
Some people would recommend upgrading the intake, but I think the stock air-box works fairly well already.
These are just some of my initial thoughts, but honestly I would just start with the oil cooler upgrade and FMIC if you're on a tight budget.
Last edited by jyeah; 01-17-2013 at 03:36 PM.