An Escort RST will get very minimal chatter unless it's been converted to EFi. The KE-Jetronic system does not like DV's as they introduce and air leak to the system that causes stalling, hesitation and other problems. You will do the turbo on these cars no damage at all by not having one and anybody telling you otherwise is a fool.

I have tried various different DV's and by far the best was to not bother so I don't have one at all and my Bailey twin piston valve is living in a box in the garage. The Escort runs at 25psi all day long and gets driven hard with no probs whatsoever.

The FRST has chatter and there is no way a DV will be going near it