93 diamante KNOCK

I have a duplicate posting in the Diamantes section...hope I'm not in trouble. Hello all you wonderful people! I have a 93 Diamante ES with a 6g72 ECI Multi 3000 (dont know how to tell if its DOHC or SOHC - all this is new to me). My problem is a loud knock from engine area that sounds like it increases in speed with acceleration. I have had some valve work done prior to this knocking noise - to the tune of $1,300 (was loosing power if i remember correctly) My BF took it to Precision Tune - also prior to knocking sound - and they suggested a carbon cleaning - $900. He declined. Well here it sits in the driveway. for 2 years. gets an occasional bath. I want it back. Have researched and my head feels like a sponge. Please advise. Thanks so much in advance

already posted in the diamante section