Engine running rich, bucks when coasting/slowing down, lack of lowend power post-swap

Got an 88 BB Mark VII and swapped in a ford crate rated @ 340 hp with GT-40 aluminum heads, E303 cam, polished cobra intake manifold, 24# injectors, converted to MAF 70 mm and A9P computer with a BBK CAI kit with bigger headers. problem is, this thing has lost a good deal of low end power(i know, its a heavy @$$ car but the stock engine had more low-end power!), its running rich (either that or im burnin anti-freeze god no), and it bucks like a mother when im slowing down or coasting. I put in a MSD coil to see if i could get a better spark but didnt help the richness. I dunno bout you but I cant even burn out (no posi yet) which i found pathetic with all ive put into it. I also had a cat-back exhaust put on a year ago. Guy who I had give it a final tuneup recommended an MSD ignition box which I planned on doing anyway but not yet, especially after what ive done over the summer: im broke as hell lol.

any ideas!?!?

thanks