yep, have used new and old ones. no particular hassles for us, but a big problem for inexperienced people. it is impossible to properly tune an engine with the sort of bits you mention, without lots of experience, a dyno and exhaust gas analysis gear.
If you are just building up an engine with all these bits, be prepared for lots of troubles to get it running unless you have a suitable Wolf map. The "start-up" maps just are not good enough.