Bernard;

"the ONE thing I didn't touch is ignition timing." ...maybe not intentionally, but you should always reset Ign Timing when Points are changed...because you always move the precise moment of ignition a slight amount inadvertently (even if you very carefully set the gap, Timing will have undoubtedly have changed a bit from the precise point it was set at before!)...but this is no big deal!...just get out your trusty Timing Strobe and twiddle it back to what it was (I like to start at 16Deg BTDC!)...and if you don't have a TStrobe, just Static Time it as described here: https://www.sw-em.com/Volvo%20Ignition%20from%20Scratch.htm#Static%20Timing

I expect that when you changed points, you changed the Timing Point to a point of less degrees BTDC...that would be consistent with a reduced engine performance and easily explain your result!...I suggest you reset your Timing by one of the methods mentioned...that will bring engine performance level back to what it was before...simple!

Good Hunting!