Turbo doesn't help anycar until mid 1st gear because the turbo is powered by your exhaust manifold...therefore exhaust has to come out before the turbine gets to spinning.
If you get exhaust, get headers. Exhaust isn't much, but the headers will help at least 20 HP.
Lighter wheels... I'm not sure what type of look your going for, but if you want looks, go with light-weight racing rims that look good on the car. Lighter wheels don't sound like much, but the ratio for an average wheel is 1 lb = 10 pounds the engine has to push.
Advanced spark plugs, spark plug wires, and ignition coil make a huge difference in response.
The list continues.. just do some research.
Peace