you use one or the other on a boosted honda. the stock ecu is not programmed to recognize boost, you'll get a CEL. and the stock map sensor only reads up to like 11 psi of boost. a missing link basically tricks your stock ecu into not seeing boost by bleeding the excess off from the map sensor...

i think you use a missing link only when you're using a vafc or one of those piggyback fuel controllers. you can get by with that, but it really isn't the best way to tune your car. kinda risky IMO. especially since crome/uberdata is free.

if you plan to tune your car with a standalone like hondata, crome, aem ems, etc...then you can use the stock map sensor to read up to 11 psi. to run more boost than that, you have to upgrade to 3 bar map sensor, which allows your ecu to see up to 3bar of boost (forget how much psi that works out to be)...

hope that helps