I

iffy - dubious, doubtful.

if you see Kate - an old saying that hides a crafty acronym ( iF U C Kate). Compare with 'see you next tuesday'.

I had one but the wheels fell off - a bizarre sarcastic reply that you give when you don't understand what the other person is saying (usually technical). e.g. "You just need to remove the overhead cam slip ring side flange", "Oh yeah, I had one of those but the wheels fell off !".

in stook - in trouble, usually in the financial sense.

inside - in prison. e.g. "I've 'eard Dave's inside again".