[91LX2Bfast]

Any aftermarket shifter is going to be better than the stock piece. As recogmended, the Streeda Tri-Ax and Pro 5.0 shifters are probably the best out there. I had a Kirban shifter on my car, and it felt very similar to a Pro 5.0, but cost less. Another option is a UPR Blue Thunder shifter. Its $135 price makes it about the cheapest billet shifter, and I haven't heard anything bad about them.
Honestly, with how stock your car is, I wouldn't worry about a bigger TB yet. Put that money towards other parts.
A larger MAF with a high flow intake will help dramatically. Although a bit pricey (~ $240,) the AFM Powerpipe it worth about 7-8hp at the wheels on the top end. I am pretty sure its made to work with a 80mm Pro-M MAF.
For your Cobra, the best bang for the buck by far is to change the rear gears. If you haven't already, that should be next on your list. 3:73's are a minimum.