I know it is a street only box but it will spark "stock" engines very well up to 7-8K. Also remember I told him to send his unit back and get the proper unit, -no big cost, and the gas savings will pay for any restock fee and shipping very quickly. Your credentials are impeccable and we both want to help the user. Your way is to use the equipment at hand and save a few bucks now, where I take the long range view and try to have the user get the proper equipment now and save mega bucks and hassles down the line.

It is much easier to tune a vehicle with the proper equipment. You should also remember I tell people they CAN get a mech adv only distributor to "work" but to get it to work "properly" they need vac advance for the street. Mileage and part throttle performance will both suffer badly without vacuum advance which costs $$$. I can also use a mech advance only unit and get it tuned to "work" on the street quite easily. Lots of experience there with dual purpose cars that ran to work during the week and down the strip on weekends. On many of those cars it was easier to pop another carb and distributor in and out tho. Remember 99% of the time any given engine is operating at part throttle. Many vehicles never see WOT!

As to why some use manifold and some use ported it entirely depends on the application and the amount of advance they dial in with mech or vacuum. Personally I run my engines with manifold vacuum rather than ported and make my adjustments accordingly. I get better mileage and cooler operation that way. I never could figure out why Ford used ported vacuum when manifold vacuum was much simpler without as many variables.

Modern cars in limp home mode using fixed fuel and timing maps get poor mileage and perform poorly. Many complain of poor starts and stalling also. Which for some is their first clue that something was wrong particularly with the older engine diagnostic systems (OBD1 etc). The fixed maps will get you home "limping" hence the name.

As to the MSD units I have spent countless hours researching the various options. I have worked in the race pits with guys trying to get their MSD or their Crane or Accel units to work. I have also seen reliable (non-advertising) dyno charts comparing OEM ignitions with aftermarket units, MSD 6A included. The OEM units outperform the MSD and other "stock performance" units all the way up to about 5000 RPM which is what the OEM's are concerned with both for advertised HP, reliability (warranty) and CAFE standards (emissions warranty again). We are not talking drag racing with nitro here or anything. I can put anything in my vehicles but I will stick with the OEM units because they perform better over an RPM range greater than my intended use. Most people run in the 1500-3000RPM range. They are also cheaper, easier to test, and more reliable.