Lately my 91 4runner v6 has been making a clicking noise that gets faster and louder with the speed of the engine. Its been getting worse and now at low rpm the engine makes a sort of sputtering put-put noise. I just had a valve job and the dealer did the head gasket recall. Also the check engine light came on saying it was the egr modulator and I replaced that but the light is still on. Any ideas what the noise could be guys?