Lost bottom end power!!!???

Can someone help me I have a 88' 5.0 with full length headers and off-road H-pipe 3" flowmasters. It has Mac underdrive pulleys and a a GT-40 intake with a 75mm BBK throttlebody and EGR spacer. I have a Chip by "Superchips" which boosts the timing and fuel pressure. It has 3.75 gears and a T-5. The car is an 8.62 1/8 mile car IF I come off the line at 45,000 with slicks. The problem lies at anything under 3,000 rpm especially on take off if I somp it right off it is pathetic until it hits about 3,000 anything after that is everyman for them self! I have tried the timing on several different settings and with and without the chip and nothing changes and I have reset the computer and everything to try to get this thing right the bottom end is stock and the heads are D00E heads. nothing fancy I don't have a cam in it yet since it is still speed density. does anybody out there have any advice on how to get the power back??? I have tried factory intakes for air intake volume and still nothing changed. the only thing that I know of is Injector size I still have 19lb injectors in it could it possibly need a bigger size 24's?? any help is GREATLY appreciated thank you..

Does it stutter on idle or just off idle? How is the cylinder compression?

Well it's not cause you don't have enough fuel. All though and adj FPR might be somewhat helpful. I would also suggest ditching the chip and tune your timing and fuel pressure manualy.

Now with the mods you listed, I bet your losing low end torque, and that's why it feels slugish. GT40 intake, 75mm TB, LT headers, 3" exhaust are all going to raise your power band, and hurt your low end grunt. Now 3" mufflers are kinda of over kill for your combo, along with the 75mm TB, too big. Actually since you said it's a dog till 3000 rpms then pulls like a mofo, I'm going to have to say that's normal.

The car doesn't studder except for the first time you romp it if it's not warmed up yet. and then it only studders only once from a dead stop it idles fine and fuel pressure is constant. the cylender pressure is withen 3 lbs on all 8 cyls I currently have the chip out and the timing on 12 is that o-k? the reason I bought the throttle body is because it came with the intake for $300 and the flows well I just like them because nobody else around here has that deep of a rumble especially since they have 3"turndown before the rearend could it be that I am getting too much air coming in and too much going out and not enough motor (Heads,Cam)? once again thank you for your info!!!

So wait, do you have 3" outlets and inlets, or just outlets? I think if you were to go with a 65mm TB you might notice a bit of a change for the better.

I have 3"inlets and outlets but the o/r h pipe is only 2 1/2 with expanded ends for the 3"flows LOUD!!!! I love it I have a 65mm TB and I will try that tonight! thanks,

Let me know how that 65mm works. I still think those 3" flows are doing more harm then good.

well the over cfming would do it.
when you over cfm your engine your going to make your bottem end all soggy and its like your eninge is bogging. though when it hits the higher rpms, heeeeelllllllo elvis.

as for the exhaust 2 1/2 shuodl work and the 1 foot of 3inch won't kill you but your losing back pressure (back pressure:awsome for torque, bad for hp), depends how you want it, low end car - a good amount of back pressure, high rpm/hp car - low back pressure

I'm back and the 65mm TB brought the sluggish down to 2,500 instead of 3,000 but it don't feel the way it did on top end...Now it seems to fluctuate at higher rpm like it is holding back or something but only sometimes like at 5,500 and farther it just feels like I have lifted and started feathering the gas it done this a little with the 75mm but now more so with the 65 the 3" flows well I changed those also since you suggested it yesterday and it doesn't seem to change anything just the tune now it sounds like every other mustang.. the 2 1/2 flows that I tried was an extra o-r h-pipe and flows as a bolt on kit so it wasn't hard to change (4 bolts and hangers) it does this crap a lot more in 1st gear is their some reason for this? in 1st as a rolling go at 2,000 rpm and me stomping it the stupid thing won't even turn the tires but at 3,500 in third without clutching it I can stomp it and blow the tires off since the car rarely sees under 2,250 it is no big deal I would just like to bring the power down to at least 2,000 if that is not possible it's o-k and I will just have to learn to live with it how about a cam?? ex>>F303???