ringing noise???

i just completed the MPFI swap on a 91 CRX DX w/ automatic transmission. took it out for its first test drive today and it works really well, better response, revs higher, etc. However, there is a ringing noise coming from the engine whenever i press the accelerator pedal. Anyone know what this is? Is it what people refer to as "ping"?

Here are the parts i used:

- 91 si intake manifold, throttle body, fuel rail/injectors, etc.
- 90 si distributor
- 88-89 integra LS automatic transmission ECU
- 91 si injector resistor box

And while i'm on the topic, what is "knocking" as well?

Ping and knock are the same thing, with ping being a milder form. They are caused by premature ignition in the cylinder. This in turn is caused by incorrect (too advanced) ignition timing, improper air-fuel
ratio, or using fuel of too low an octane. A mild ping heard on hard
acceleration or steep uphill climb generally is considered harmless.
Continual pinging at constant speed or heavy knocking (you will hear a
loud noise and ususally feel the engine shudder) are considered bad and
can cause serious engine damage. Burning of valves and pitting of
piston tops are possibilities. So you probably have you distributor advanced to far forward, and you need to back it off some.

is it a metalic ring? like a funny kind of sheet metal ish sound? that is a common sound on civics when the cat's heat sheild gets loose (mine did it) check that before jumping to conclusions. Also, a metalic ring is a common sound with aftermarket exhuast without a resonator, it could be that too. I guess i'm saying we'd need more of a description of the sound to tell.