You didn't say how many miles were on it but since its an 01 its could be likely your engines just flat wearing out. BUT It could be a few other things tho so check these first: Have your fuel pressure tested and replace the fuel filter or fuel pump if needed. Check your injectors as a dirty injector could easily cause this. Also check your throttle body, mass airflow sensor and spark plugs. If any of those are gunked up it clean them up(check for Make your can run better with spray cleaner on Scottys Youtube) if their dirty it could cause this and finally have your battery and alternator tested if either are weak it could cause probs like this and I assume you have a clean air filter since your been replacing things chasing this down.