Break-In. How Long?

I fixed a Performance Issue with a Ballast Resistor!
The First Time I gave 'er the onions it revved well up to about 3 1/2 r's and started to stumble and miss...
Runs Well at W.O.T. to 3 1/2 r's and then runs like s**t,
I've thought about this all day... wondering what did I change that caused this?
I got a Halifax Distrib, Accel Wires, NGK Plugs and an Accel Yellow Coil. I tried to match the Coils resistance with an Equal Resistor @ around 1.6ohms (Too Much!)
I put My Old Resistor (.7 - .8) back in there tonight, changed Nothing else and Bam! She Runs Like a Striped-A**-@pe!
Now I just have to summon the nerve to run it passed 4xxx R's... 3rd gear at 4000 rpm was about 75mph and Loud! Lol Too Much Fun!
eek,
I'd make sure you know how much mechanical, and vacuum advance the distributor is giving by using a dial-back timing light. If there is too much full total advance, it could cause missing at 3500 rpm and maybe damage. Make sure the distributor has the right advance curve. Do not assume it is right.