1992 Chevy S-10 oil pressure

I just had the oil changed about a month ago and still have until 5/4/08 before I need to have it changed. Yesterday I changed the acumilator and compressor, also flushed the system(AC) and changed the orphus tube, then added new free on. The ac blows great. But now my oil pressure seems to be lower than before. I check the oil level (while its cold, and also while its hot) and the level is within the reccomended area of the dipstick. The thing that concerns me is that I see my oil pressure guage at around 40 and it drops to about 25 at idle. I dont know if anything I did while changing the ac parts might have messed with anything to do with oil pressure. My guage has three marks. 0, 40 (middle), and 80 (top). The oil pressure used to normally stay between 65 and 80 but after all the work I have just done yesterday, the oil pressure doesnt even hit 50. Is this a problem to worry about? And if it is how do you reccomend I fix it.
thanks
Bobby Claxton
Bclaxorlando@hotmail. Com