I recall some older threads about the pros and cons of removing the Thermactor. I did a search and couldn't find them. I have an 88 F250 with a 460 EFI. Apart from the removal being illegal (wonder if the NSA is reading this thread now!), what are the disadvantages of removing it?

Thanks!

 

I lost 2mpg after removing mine (reluctantly), and had 0 gains performance-wise.

 

The thermactor system just supplies fresh air to the stock cats to aid combustion, if those cats are gone(they should be at this age) the system has no usefull function whatsoever. Downsides of removing the system only result if done incorrectly, all vacuum lines must be capped or removed, the TAB and TAD solenoids must remain electrically connected, and there can be no leaks in the exhaust system upstream of the O2 sensor so all plumbing should be removed and manifolds plugged or headers installed.
On the other hand if there are no leaks in the plumbing and the air pump isn't seized there are no gains from removing the system.

 

Thanks for the feedback from both. I'll go ahead and keep it.

Another question, I did read where they were designed to cause a burn of exhaust in the exhaust manifold. Mine seems to only pump into the catalytic converter. I couldn't find a place where it was pumped into the exhaust manifold. I'm only asked because it wouldn't surprise me if the previous owner removed that.

 

An HD trucks(F250 and bigger) the design included a tube at the back of the motor connected to both manifolds right before the collector flange, it would be pretty hard to see from anywhere except directly below or behind the motor.