Originally posted by Joel87GT from 4gcelica.net The catch can methods is used to catch oil deposits from being recirculated and sludging vacums lines within the intake manifold, intercooler, and Throttle bodies. FRAM G3 Fuel Filter faced in wrong direction, it should face the other way. Parts Needed: FRAM FUEL FILTER - G3. Tools: Sissors Tube clasps. 1. CUT your PCV in half. The fram fuel fitler G3 comes w/ its own clamping glasps to fit the tubing of your PCV hose. 2. Take equal lengths of each PCV hose and install at each end of the G3. Use clamps that come with G3 kit. 3. measure and cut the length to accomodate the PCV/G3 between Blow Out Tube from Valve Cover to Throttle body. 4. Install in proper blow by gases direction indicated on Fuel Filter from Valve Cover to Throttle body. 5. Finished. he result of a CATCH CAN is to keep blow by gases clean from tarred sediments deposits in VC, T/B and Intake Runners ports. Picture of my Valve Cover after 10K miles. Conclusion: Your engine will re-breathe at bit better. Improved gas mileage too. All bad emmission deposits will be caught in G3 fuel filter. Replace when you see G3 20% saturated in oil. Notes: PCV (Positive Crankcase Ventilation) system is used to vent the excess pressure. Back in the olden days the PCV was nothing more than an open pipe at the top of the valve cover with a filter attached to the end to prevent debris from entering. However, primarily for emissions reasons, newer cars have been made to recirculate these blow-by gasses back into the intake. This system uses the vacuum produced from normal engine opperation to draw air out of the crankcase and re-combust it. This system generally works fine, but it has two notible drawbacks. 1) Since the PCV system begins at the top of the valve cover where there are many fast-moving lubricated parts, a certain amount of oil mist gets generated. This oil mist is then drawn out of the valve cover along with the blow-by gasses and eventually line the entire intake tract with oil; which on a turbo car, besides making a mess, also coats the intercooler with oil and reduces its efficiency. (you can install a pcv oil catch can, or vent to atmosphere to solve this problem) 2) Since the PCV system depends on the intake vacuum to draw air out of the otherwise sealed system, if the PCV piping gets bent, kinked, or otherwise obstructed, the PCV system will fail to function, causing pressurization of the crankcase, and subsequently poping the dipstick. On a properly functioning recirculated PCV system, you should be able to feel vacuum from the dipstick hole if the dipstick is removed while the engine is running. Also, you should notice a slight resistance in attempting to fully remove the oil cap with the engine running. Aditionally, removal of either of these two items on an AFM-based system (4th gen celicas) should cause a fluctuation of the engine idle speed due to intake air being improperly metered.