Do I need a programmer?

[Stytch]

Basically running a stock 450 right now. I just ordered and FmF power core 4 slip on and the only extra I've purchased is a Twin air replacement filter (so I wouldn't need a programmer). Would I need a programmer if I only purchased a slip on?

[Duster]

No, I am pretty sure you will not.

You'll just have to try and see.

[georgiakfx]

you should be good, I have been running a pro-circuit slip on and uni filter with no programmer for over a year now

[Duster]

Yeah, I'm running a full race exhaust, gutted air box, and No-Toil filter.
Still rich.

But I realize now the ECU is really questionable on how it is operating and metering fuel.

He'll just have to try it and use some common sense to judge if he's running lean I think. A small amount of leanness can be cured by increasing the TPS output voltage a tad. But this enriches the entire throttle range and is limited in function.