Hello all. Jst want to thank you in advance for any input you may have as everyone on here is so helpful when I have a question.

Anyway, here it is.The Car.
69 Camaro
355 sb
64 cc Aluminum head
flat tops.about 10:1
Comp Cam #12-225-4
.555 lift and 262 duration @ .050
lobe sep 110
cenetr line 106
roller rockers
Msd ignition
Dual plane intake w/ 1 inch spacer
Holley 750 dp hp series
turbo 350 w/2600 stall
3.73 rear using 275/50/15 tires M/T street slicks

Car runs great. Get in, pump the gas 2-3 times starts perfect and runs like hell.
No stumbles, boggs, missing, nothing. BUT it is running too rich and the gas mileage is about 5mpg on the street which is TOO poor.
I don't drive it much and to honest really haven't done much in the way of adjusting anything but now is time.
The other day I punched it from a stop sign(being a little kid) and took notice to a cloud of black smoke in my mirror. (could be my gas milage problem.) And it just plain runs rich at a idle for sure. Now I did do some adjusting with the vacuum guage and the idle screws, but I am thinking it has a power valve issue. ( I would think a 2.5 valve) would be ideal for my application but wanted other opinions. ALSO...This is important. I noticed my oil presure isn't as high anymore as it use to be. It is about 40psi when first started, but after a few minutes it drops to about 9psi at idle idle is @ 900rpms. Now it goes up about 10pse per 1000 rpms, but I am thinking my rich mixture is blowing feul by the rings and into the crankcase and thinning the oil. NO, I didn't check the dipstick yet or smell it, but will this weekend and change the oil.
My main concern was about the powervalve, and also, do they have 2 power valves in the double pumpers? I only rebuilt 600's before. I would assume there is a power valve in the rear metering block, but haven't look into it yet. Info is welcomed.

Again, car runs great. BUT the gas milage is WAY to poor for what it is and it has a RICH mixture problem. thanks guys.