Sorry but I am speaking from personal experience and I saw no negative side effects from doing this. No loss in gas mileage, no erractic idle, no hard starting, no CEL. Not only did it work for me, but several of my buddies that have/had 89-93 stangs. Theory is sound but some times you have to put things into practice. Besides that, look at the money you've spent. This is a Junkyard thread. I picked up those housing (which are plentiful) for 5-10 dollars.
Don't take this the wrong way, but that's not a convincing argument. Just because the CEL isn't on or your car has no detectable issues doesn't mean everything is fine. Until you put the car on a dyno and map the A/F ratio and compare, you have no idea if you are running too lean or rich.
In other words it might work fine, but not ideal.