New Stang With A Problem

So I inherited my cousins stang last week. It's a 95 gt with nothing done to it, completely stock. So me and a friend went out to where everyone tends to race on this abandoned road like 20 miles out of town. Since I have really never driven anything more then a 4cyl I wanted to play around for a minute. I was nervous about stepping on it since it's a bit stronger then my jetta. But I decided to see how fast and how quick I could go. And here's where the problem begins.

I stepped on it in 1st from a dead stop and when the rpm's got to about 4500-5000 I heard a horrible sound coming from the engine. It sounded like taking a chop saw to metal and some gray smoke came out of the exhaust and it had a small smell of sulfur. I stopped cause I didn't want to cause any further damage. I know a new radiator and t-stat have been installed and that's it. Anyone have any idea what this could be.

Same thing happens everytime. I floor it, gets to about 4500-5000 and makes that sound. It will do it in 2nd as well if I let the rpm's get high enough. Forgot to mention the temp jumps a bit, like if it's at 'O' it will jump to about 'M'.

TrueBlue95GT said:

Any more symptoms? Is there a check engine light? When this sound happens, do you feel it? Loss of acceleration, jolt? Does it make this sound when you rev it standing still?

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No other symptoms. The check engine light is on I just haven't had time to get codes ran. I don't feel the sound and it really doesn't seem to lose too much power, maybe a fraction is lost and that's about it. And it doesn't do it standing still. I know I need to get codes ran, but I figured maybe this has come up with someone before. Been on these boards a while just never registered until now.

So I went out and got a code reader and ran the codes. At first it pulled code 539 but that was cause the AC was still on. Turned it off and ran it again and it just said System Pass (111). So no codes are there.