I'm by no means experienced in these matters, however my limited experience tells me your approach is all wrong! If your looking for quicker lap times, you need to focus on these three key aeas:
1/ Your driving ability - no matter how good you are, this can ALWAYS be improved, and this is the one thing that will have the largest effect on your lap times
2/ Your tires - spend the money on decent semi slicks, RE055's for example
3/ The weight of your car. Strip it out as much as possible.
First thing i would do is go to an Advanced Drivers Course or three at Mondello, get an expert in your car and see what they can do with it around Mondello. This will give you something to aim for!
Just looking at the Mondello website, the track does appear to have a few long straightaways. However, cornering skill/ability, braking ability, and acceleration out of corners are all cruicial to good lap times, and none of these things will eb improved by a turbo or supercharger.
Assuming you are at the limit of your cars ability in it's current trim, and assuming budget is not an issue, then a full TRD house NA motor would be my weapon of choice, however not knowing what Mondello is like, perhaps a good supercharged setup might be just as quick? *shrugs*
If you just want power, turbo is the answer. A well engineered turbo setup can also give the balance of a supercharger setup with less weight penalty. The few turbo setups i have driven were somewhat laggy, hence i favour supercharger, but if your just building a track car, NA all the way IMHO!
im not just building a track car! i want a road car dat will be radid on the track an pretty gud to drag 2