So this problem just started today. At cruising speed my oil pressure gage is about 50psi (according to the gage) and stays there. When i give it more throttle the gage drops a little and then goes back up. It drops even lower if i floor it. but no loss in power hower i noticed when i hit about 75mph i feel a hesitation or miss or stumble or whatever else youd like to call. and it repeats it self every id say 5 secs. when i go back to 55-60 its not there. i also noticed pressure drops when tranny shifts gears. and then goes back up. but im worried because this has never happened before. gauge usually stays around 50 psi and would go down a little at a stop. but now its goin back and forth back and forth and i dont know where to start. no smoking, no leaks, oil level is fine, idels fine, drives fine. any thoughts and opinions would help.

i didnt have alot of time when i posted this thread so i wanted to share a little more info about the car. it has 53000 miles and unfortunately i had to replace the engine because of a cracked block back in december (purchased and installed factory replacement from chevrolet) the top end is still original (tb,plenum, intake, runners, etc.) for the past 3-4 months ive been dealing with a high idle issue with my car. after replacing sensors and what not i came to the conclusion that mabye it was the tb itself. i had a bbk 58mm so i swapped out the tb's. also when i did this i had read on a post about a tb coolant bypass, so i did that as well. really didnt feel a difference other than the tb getting extremely hot after driving. so this past friday i put the coolant hoses back where they belong, reset the ecm, and when i started the car, nothing but white thick smoke poured out of the exhaust and coolant was spraying everywhere. turns out the iac gasket blew and coolant was getting sucked into the throttle body. so i pulled the bbk, and after cleaning the factory tb, iac, and passages, i replaced the gaskets and installed the factory tb on the car. i had a hard time getting the car to start and when it finally did it smoked for a good 30mins at idle, after that it stopped, i took it for a test drive and car runs even better then before, and idles perfect now. infact it was ideling too low and stalled a couple of times, i adjusted the minimum air and fixed that problem, now that brings me to yesterday, my oil gage is going bezerk and im getting a pulsated stumble when i hit speeds over 70mph. im changing the oil tomorrow which is obvious i should do. is it possible that coolant got into the oil and thats causing the gauge to go crazy, would that also cause the stumble i get at high speeds. sorry for the long post. one more question. when i have the oil changed would it be alright if i used mobil 1 5w 30. thanks for your time and help.