I need to replace the valve seals on the TFS heads on my '94 F-150. I was planning on buying the air fitting at CarQuest to pressurize the cylinder when another mechanic cautioned me against that method. What has your experience been with that method or others for removing springs while the head is still on the block. Also do you folks recommend Viton positive stop seals. I apologize if I missed this in a previous post but my computer keeps crashing. Thanks.