jedi0_3

Morning all.
Mk4 Escort XR3i EFI 1.6 CVH.
Recently changed oil and filter and also changed sump.
Original oil was 10 40 semi synth from local motor factors which was fine and gave good pressure but changed to Mobil1 Semi Super S 10 40.
The first time I started the car up following the change of sump/oil/filter it sounded a bit tappety and the sump leaked but had to use the car for a couple of days before I could re-do it properly. I drained the Mobil oil and fixed the sump but had to re-use the 2day old Mobil1. Now when I start it up the oil light stays on for about 5 seconds and needs a couple of revs to turn it off, once it warms up it's fine. Never done this before though and thought the Mobil 1 oil would be better for it. The dip stick reading shows there is a bit too much oil in it, could this cause the problem?
I have also noticed when slowing down for a turn by taking foot off the accelerator I get a bit of a popping from the exhaust, is this back pressure and is it a bad sign-worn rings?
Thanks