if it needs a tune up i will misfire and run poorly and not turn rpms like normal, and fail to make boost.
if the cats clogged it will kinda sound like a vacuum cleaner with a full bag when you floor, and have no power. the cel can flash when its floored as well.
it could also be a bad bbv or a vac line. spray the bbv the map sensor and the all the vac lines with carb cleaner, if the idle jumps up you found your leak. you can also spray the sc to lim injectors and tb gasket area and the egr tube looking for a leak.
