Loss of power . . . more info

[SheStang87]

Thanks for everyone's help. My car is a five speed, Tremec 3550. I've been shifting around 5600, I've found that a good point for her. It may be a bad clutch, I'm putting a new one in this week end. She is just about stock except for the tranny and gears. It's not completely cutting out, but I've noticed a decrease in her power, it takes a while for her to tack up. My 60 foot has dropped from a 2.2 to a 1.8 when I put the gears in, she pulls pretty hard in second too, third gear it is obvious that it doesn't pull as hard. I've even had someone come up to me from the stands and say they've noticed it too. I've played with my timing and found that 13 advanced works good for her, I've tried other points and lost time. I found that when I opened up the box where my air filter is, it helped a little. I took out that air horn thing too. I was thinking that maybe she needs more air and/or fuel. What do you guys think?
Thanks alot for everyone's reply, I didn't think to put out more info. I hope this helps.
Thanks again,
Chirstina