85mm MAF- Which is better
tb bypass
lid
New Valves
New Springs
Pushrods (I have seen people say that they can feel a difference) ...
what a joke! Yeah, there is a difference. you might be able to mechanically over-rev more than one time without having a couple pretzels come out of your top end! 
Exhaust tips
Removing cats
LS6 cam.
That was a joke. No one take offense. I don't know about anything tune related. It will change a bunch of stuff at one time. It is probably something that you will actually notice.
ported tb
bigger maf
descreening your maf
K&N filter
putting NOS octane booster in your gas tank
feel free to add to the list.
tb bypass
lid
tune on stock car
switching to Flowmaster muffler (actualy you might be able to feel the car being slower)
Cold air intake kits
K&N FIPK
Ok all that's worth a good 20 rwhp. Why? Half parts, and half tune. Everything is always in the tune. If you can't feel 20 rwhp then it's time to hit the gym because chances are your car is overworked and sick of hauling your fat, 350lb *** around, which is why it's no WONDER you can't feel anything. You probably couldn't even feel a 250 shot if it froze your dick off.
anyways, my fat 180lb *** could only get my bone stock automatic with 130,000 miles on to 13.2
I can swap the 85mm SLP hunk thats on my car now for an 85mm truck OR Z06 MAF and I can see the grams/sec. change and the a/f gets all screwy....SLP modifies their MAFs with some sort of resistor.
The Best V8 Stories One Small Block at Time
I definately felt a difference with both my TB, and MAF, on separate occations. Was it huge? No. Was it tangible? YES.
It's all about AREA UNDER THE CURVE, not a meaningless peak number.

A MAF sensor AND ported TB gain area under the curve, THAT's why you can feel throttle response pick up with both modifications if you know what to look for.

