hi
as mentioned is a good idea to give them a good clear out once in a while , mines a 2.7 V6 and also give mine a good clear out as once in a while
the map sensor are one of the favourite things to block up , they need to be removed and cleaned out ,
i personally use millers cleaner
indeed gettting the codes is the way to go, i like many others bought my own, bought one made by Gap and called an iid , they are around £420 but will tell u in great detail of all the systems inc live data
as also mentioned get them all cleared, then see what comes back up
if it's still under warranty get it booked in with them, also ask for a full code print out, before and after they are cleared and get them to check the live data , as this will also test ur map sensor, egrs , injectors etc
hope that helps