"oink" noise from engine, only sometimes

[whiteboyay]

Hey Guys,
I was hoping to get some of your expert advice on a noise that is coming from my '93 mt 4a-fe. I just recently spent $900 on the car changing 3 motor mounts, slave cylinder, master cylinder, exhaust manifold, cv axle, and a spindel. It runs smooth and quiet. Sometimes though, when it really picks up the rpms, (no tach so dont know when....i am guessing around 3000), it will make this "oink" noise. Just say "oink" slow and drag the word out for about 2 seconds. This is how it sounds. It is coming from the engine bay somewhere and it sounds like it is from the passenger side. Again, it only does it sometimes. If it does it any, it will usually will do it at that same point in the powerband for 1st-3rd. 4th and 5th I do not recall it ever making the noise. Also, once it starts at that point if i keep going through the gear it will do it intermittently 2 or 3 times. It is really strange and I have no idea what it could be. Thanks guys.

[TI-CAVA]

is it like a knock, hitting something?

metal metal?

metal plastic?

internals?

maybe u can record a video w sound so we can help u better

[whiteboyay]

That is what I am not sure of. It is actually coming from somewhere in the engine. It sounds metallic, not plastic. Depending on how fast i accelerate, the "oink" is faster or slower. It seems like it comes from different places sometimes. Sometimes to the right or the left from somewhere inside the engine bay when I am driving. It is just so weird, if anyone has idea let me know. I will try to record it if I can. Thanks.