Loud Clanking Engine after P0401, 2000 Ford Ranger V6 3.0L

2000 Ford Ranger XLT V6 3.0L Flex Fuel stick shift.
Was getting code P0401 "EGR Flow insufficient" for four to five days.

A few days later no more check engine light, but loud clanking at startup, idle, speeds above 50 MPH. Oil pressure guage going crazy at idle. No evident loss in horse power. Good oil changes regular maintenance. 107k Miles

Could it be carbon deposit blocked EGR valve, then found it's way into engine.
Or is rod bearing more likely?

Also does anyone know if different engines can be used?

What's your best suggestions?

difficult and costly engine rebuild

Rebuilt engine price $1400.00 to $2000.00

Used engine price $600.00 and up

Transmission and drive belt tentioner recently replaced

Thanks for all your help!
~ andyd5@hotmail.com

Just an Update on my progress. I have yet to find what caused it but found a used engine with 35k miles for $860.00. A good deal if it all works well. pulled out knocking engine transmittion comes with thanks to bolts going both ways between block and tranny grrr. It wasn't an easy removal everything was lock tited in place a few months ago when the clutch and flywheel were replaced by mechanic. Assembled engine and tranny back together and dropped it back into place. replaced intake manifold gasket, thermostat w/gasket, new oil filter, new fuel filter, new air filter, and replaced nearly every hose except the heater hoses couldn't get them anywhere before next weekend. Everything looks good Just have the a/c compressor, radiator, fan and drive belt left to reinstall before the fluids then a start test, so far so good already have a good compression pray the used water pump is in good shape. If anyone knows of anything I should be aware of please let me know. Keep in mind I am not familiar with computerised engines. I used to love working on my '89 Ford Probe AKA wanna be Mazda.