need help picking an oil weight/viscosity..

[jetuomi]

hey, I've been enjoying the few nice days in March by taking the car out and enjoying the open roads..

BUT, I've noticed something a bit strange.. I know the stock oil-pressure gauge is crap, BUT, I'm getting these results:

I get better performance (seat of pants), no pinging (if I use 89 octane) and less vibrations coming through the MAC shifter if the needle on the oil-pressure guage is at the right-side or R, and I get slighly worse performance, some pinging a 5 grand, and lots more vibrations coming from the shifter if thte pressure is higher than the righ side of M... Also, at this pressure, I get that crap-gas idling sound (like its pinging) at idle..

now, the other thing is that the pressure is lower when the temperature is colder, which makes sense, but, is that an indication that when the temp starts to rise (and especially at the track) that I should step up from 10W30 oil to something like 20W50 ?? (is that the viscosity?) or is there something in between?? My block has almost 125,000 miles on it, so time to move upto a heavier oil??

Any ideas?? (sorry for the long post!)
Thanks !!