My car kinda acted like that when it had a fried spark wire.
It would be kinda sluggish until 4k rpm then it would take off like a "rocket". seems kinda like what your experiencing only backwards heh.
Hyundai replaced the wire for free, but wanted 90 bucks to replace the plugs. lol

 

You bet. I'm waiting for Chris to finalize the Hotshot deal before I jump in. I've got a nice Catco cat I'm looking at too.