Thumping sound through intake help!

Hello,

I'll get straight to it, I've had a loud thumping sound through the intake for some time now and after doing alot of research I decided the camshaft was worn and the lifters were worn out so I decided to order some hardened lifters I spent the week stripping the top half of the engine apart I ended up replacing the head gasket and the lifters even though they were fine I didn't end up replacing the camshaft because it looked like new barely any wear at all certainly not enough to cause a problem,

So I've built everything back up and still the same thumping noise remains and I was wondering If anyone could help me out, thanks for listening I look forward to hearing your suggestions