Well I haven't actually got anything installed on my car except for a trust airnx II panel filter, but I'll offer what I know so far. First question is what corolla you have and what engine? 1zzfe or 2zzge? or maybe the more older engines such as 4age, 7afe, 4afe, 4age (20Valve), 4agze, 4AGTE... If you have a 2zzge its better to get the factory exhaust manifolds ported as they provide the best gains as we speak. With exhaust manifold, 4-2-1 provide better mid-range power output which would be beneficial for everyday driving. Go for 4-1 if your after outright power. Cheers