I am thinking of removing my stock cats and replacing them with a 3" high flow cat from Jegs and then running 3" back to a 40 series Flowmaster and exit infront of the right rear tire. has anyone done this or heard of it? How complicated is is to remove the stock cats? I saw another post that said there were 2/side on which is internal to the pipe before the main cat, is this true? Will increasing the flow by 45% cause a serious drop in torque/ increase in Hp?

Thanks for the input in advance.

 

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Welcome ! They're probably confused on how you would remove the 2.5" dual-headpipe/multi-cat configuration and replace the entire thing with 1)3" aftermarket cat. Typically, this mod is done with 2)2.5" aftermarket cats; 1) in each headpipe, before you go to the single 3" system. Next, why create a high flowing exhaust system that is choked down by a low-flowing, chambered Flowlaster 40? Lastly, yes, that sounds like a system to reduce low-end torque and streetability and replace it with top-end, WOT power.

 

I have just done this to my 2001 F150 Supercrew. I had the whole exhaust dropped @ exhaust manifold. From there the pipe was cut about 8 inches from exhaust flange. We matched up the size pipe and ran true duals into 2 Flowmaster 40's. The pipes were then ran out in front of right rear tire, like the lightning, with 3 inch chrome tips. NOTE..... You will need to purchase 2 O2 sims for the down draft O2 sens. These connect in between O2 sens. and where the O2 sens. connects. The best way to put the O2 sens. back in w/o alot of work is to buy a couple of spark plug antifowlers and cut off the end of each, cut a hole big enough in the pipe to fits the plug into and do spot welds over and over as to not melt plug and just put in O2 sen. when it cools off. The other thing is placement of the flowmasters. Just place each one side by side but off set and you will be able to utilize the area and heat shields where the factory muffler went. This set up will give you alot more top end but some loss of torque. Other noticable things are the rims gets alot of soot on it and I have been told this will harm the rim by a mechanic for ford. Other lightning owners have said it doesnt. There is increased cabin noise. Other then that it sounds bad as hell