Acceleration issue

[GettaRobo]

I've been having an issue with acceleration since I bought my 88 NA last January. It more or less runs fine up until 4k RPM's (perhaps a bit sluggish even) and then it won't go past WOT or otherwise. I'm getting black smoke out of the tailpipe too from what I understand is from too much fuel. The isn't normally black unless you pin it, but it definitely smells rich at idle. What has been done/checked: sparkplugs twice, coil wire, MAF has been replaced, tuneup has been done twice, TPS has been adjusted and replaced. As far as I know there are no holes in the intake, but I'm not 100% sure. Only one error code displays, but it is for the speed sensor in the transmission (another problem which deserves it's own thread in itself.) There is also a possibility of a vacuum leak as I can hear something sucking air when I turn the car off. I'm wondering if anyone has some insight with this problem.