One of the plugs may have got broke when installed, or the could be crap pugs - what kind, brand were they? Also, with higher rpm's, at more than an idle, the coil wire is probably arching through the tape you put on it. And yes, it's very easy to get the plug wires on the wrong plugs, as the Blazer has a weird firing order. I imagine the coil is ok. Replace the plug wires, the coil wire, dist cap, rotor, etc, and see where you're at. As suggested, check the vacuum lines.
Most people on this board suggest Delco for a dist cap. Some of the after market stuff is crap. You should do a search on this board for "tune up", before buying any parts. Here's a good
thread to get you started.
Keep in mind, the codes do not indicate the is part bad, it only gives a direction to go when trouble shooting.
P0101 = Mass Air Flow System Performance
P0300 = Random/Multiple Cylinder Misfire Detected