I have no doubts that Ramzi Yousef had Iraqi links and that Saddam was involved in the FIRST World Trade Center attack.
However after that there is only circumstantial evidence linking Iraq to any Al-Qaeda activity in relation to 9/11.
Saddam was a crafty bugger who outlasted two Presidents. He knew that by the time President Bush II was elected, his time for farnarkling about had well and truly passed.
The lead hijacker being witnessed meeting with Iraqi intelligence in Prague a few months before 9/11 may not be definitive, but I'd call it a lot more than just "circumstantial".
The Baluch Connection: Is Khalid Sheikh Mohammed tied to Baghdad?
Khalid Sheikh Mohammed's Account Links 9/11 to '93 WTC Attack