Low end bog, high end gear drop?

[FlyLike-a-G8]

So to start off I bought an 08 GT for what I previously thought was a good deal. 102k miles few minor fixes its but I was going to dump a bunch of money into making it what I wanted anyway.

Straight to the point: Between 1-2k rpms the car feels like an anchor was thrown out the window. I can literally feel the car slow and speed with rotation of the crank. it does this in drive, and sport but not manual shift as I keep the rpms higher. then to add to my already nervous findings of the car, when I step on the gas (because the bogging starts to piss me off) the car will slam into second (i mean slam hard, jolts the driver) and accelerate like a bat of hell.

the scary: the person I purchased said car from said he replaced the computer, and i'm starting to think this is a water damaged car with a clean title and I bought a lemon.

What I want to know: before I go 5k into parts purchase, is this a common problem? could it be a dead lifter? how can I ensure the car is worth building prior to the actual build? (I do plan on getting it bore-scoped before doing the dod delete and heads)

any help or input appreciated.

[STL_G8GT]

Has the car been tuned?

[FlyLike-a-G8]

to my knowledge, no. Judging by the guy I got it from...it was purchased at auction and done the least amount of work possible to flip.

[norm8332]

There is a possibility that this is a cat issue, especially if the car has been tuned. Low end power goes first when the cats start plugging up. Sometimes a rotten-egg smell at the exhaust can also be noted.

[FlyLike-a-G8]

hmm it does have an offroad xpipe, I haven't noticed any smells. appreciate the help, I'm going to look into this...if this is the problem that would take a lot off my mind as I'm doing an essential ground up rebuild. thanks again!

[roman1978]

does it feel like flaring ?

[J Wikoff]

Take a good look at the air intake for leaks, and maybe give the MAF filaments a good spray with throttle body cleaner.

[FlyLike-a-G8]

So I'm not actually worried that the car is doing this right now, I am worried that the problem will be an issue with the mods I have lined up. DOD delete, ported and polished heads, kooks longtubes, and a few more (as money is saved). In conjunction with this post, I am looking for guidance on upgrades. I'm currently looking to get in the 550hp range on motor. (e85, and forced induction may come later.)

[-Ray-]

So I'm not actually worried that the car is doing this right now, I am worried that the problem will be an issue with the mods I have lined up. DOD delete, ported and polished heads, kooks longtubes, and a few more (as money is saved). In conjunction with this post, I am looking for guidance on upgrades. I'm currently looking to get in the 550hp range on motor. (e85, and forced induction may come later.)

If you are going boost, pick your cam wisely.

[J Wikoff]

You know, that sounds a lot like what my old Bonneville does when the MAF screen is removed.