Since using oil flush & changing sump gasket on my 1990 XR3i EFI the car rattles like mad on start up and oil pressure light stays on until the engine is reved a couple of times.After about 30secs-1min it sounds alright. After a run & Left again for 10mins before restart oil light stays on after start up again for a few seconds. Pressure is about 30psi@1000rpm and 60psi max at approx 3000rpm from cold and was staying around the 25-30psi warm but coming down motorway tonight was only showing about 15-20psi at 60-70mph and oil pressure light flicked on once coming off sliproad up an incline!
Has brand new 10-40 oil, level is fine but not sure on pressure gauge accuracy as 5yrs old but like I say has sounded terrible on startup since the engine flush & new sump gasket-was fine before I touched it which leads me to believe it is oil starvation.
Fitted recon block & new non Ford oil pump 2yrs ago with new lifters and cam was fine.
I did take the oil pickup off to clean it during sump gasket change, is it possible to put it on wrong?Is there a way to find & clear a blocked oil gallery?
Anyone got any ideas before I tear the engine out?

 

it could be pickup pipe gasket seal, espesially if u had it off