Knockers are killing me- Help!
 

Help! My 1990 5.0 purchased new in 1990 with 83k on it and bone stock has always run like the wind; perfectly. now all of a sudden, under WOT my boys are knocking near the end of the rpm range, around 4000-4500. Have always run 87 octane and never had a problem. any ideas? bump the timing up help?

How long has it been since it's last tune up? I suggest a Full tune up: fuel filter, plugs, wires, pcv valve and filter, etc... some injector cleaner too maybe and let us know.

Never tuned up. K&N filter may also be dirty. could that be it too?

Absolutely, it can get the MAF dirty and the car not run properly also, go for the full tune up, clean the air filter and the MAF too, good luck let us know!:D

If you advance your timing, you will have to increase your octane. I run mine at 14 degrees (stock is 10) and have to use 93 octane. On a bone stock motor you should run high octane anyway according to the owners manual. There are a few stages of detonation, pinging, knocking, pre-ignition, etc. If it is mild, you won't hear it, but it's still happening and causing some damage. Do the tune up first.