Ive been aware of them for over 30yrs. The first hopups for the first EFI HO mustangs were a 255lph or even a 340lph fuelpump and an octane rod .......
Also changing the timing chain degree setting and you get an instant 75 hp increase without touching anything else other than the tune and that sometimes nets between 10-25hp more..
I make my own.................
Another tip is concerning this thing in the pic below...When you replace the distributor to anything other than a Motorcraft and dont put the motorcraft reluctor wheel in the new distributor to keep halls effect accuracy for each cylinder the company who manufactures them isnt privy to Fords technical notes and the teeth are too wide and spacing between the teeth are too narrow and that messes with the parameters burnt onto the chip in the ECU causing all sorts or idling problems...
The proper sizes are.......
Large teeth — .398 to .400
Small tooth — .258 to .262
There should be even spacing between the teeth with the exception of the long space following the narrow tooth.
My large teeth varied between .405 - .410 and my small tooth was .267 wide..I made all large teeth .399 and my small tooth .260...
It just takes a file and some common sense as to which side of the tooth needs filing and how much.
Theres also a way to do a similar method by simply unpinning the dist gear and turning it on the shaft 180* and repinning it. That will change the setting between the pickup at falling edge and TDC by 12* earlier as theres 15th on the dist and 15 into 360 is 24 so on side is dead on with a tooth and the other side splits two teeth so gear placement is important too.......
Good Luck