Hi Charles.
If the plenum as flooded then that is where the water as got in, on some of the earlier models the centre partition will be there, if this is the case water can and will collect on the OS part of the plenum.
You need to get under the car and check both plenum tubes and cut about 20mm off each one, I cut mine at a45 degree angle this is not required it is just the way I like to do it link below.
Cut off the first little section in photo one in the link which is clogged up.
http://www.the75andztclub.co.uk/foru...ad.php?t=84865
http://www.the75andztclub.co.uk/foru...ad.php?t=86684
Also have a good read through this link if you have not done so already.
http://www.the75andztclub.co.uk/foru...89&postcount=1
If I was you I would not glue anything in place and do not put anything into the main plenum chamber, purchase a jules plenum guard for the OS wing area.
You could also do this below as a belt and braces
http://www.the75andztclub.co.uk/foru...6&postcount=19
The scuttle screen panel can also leak.
http://www.the75andztclub.co.uk/foru...3&postcount=61
The spy hole mod
http://www.the75andztclub.co.uk/foru...1&postcount=21
Sorry lots of link but quite a few members will get caught out with this really wet weather we are having, and there is more to come, good luck Arctic