Problems with my Civic Si 96

Hello ive been running into problems with my 1996 civic si it has a b18a engine and a GSR head my problem is when i am driving and going up hills i lose power not like lights.. i mean in torque like it wants to go but it cant.. ive been trying to figure out the problem.. it happens alot in the winter but in the summer it may only happen once.. i may be in fourth gear and i would have to shift down to keep my rpms up.. i barley make it up hills with the car..

now since then.. i found out i have a loose muffler that shakes.. since the car is so low.. i was told it mite be because of that.. can that be the problem like im losing force to go up hills?


can anyone please help me..
thank you so much for your time and interests as much as I am with civics!


Tommy
http://i3.photobucket.com/albums/y65/TommyMidnight/30948990007_large.jpg

a loose muffler wouldnt do it.. sounds like a plug wire..or sounds like 3 cylinders.. check spark